TA 

681 

.J13 






il,l;;,.piasi 






illllilllllllj 



I 


|!| 


■ 


ma 



mmi iiiii! 



I' IP' 

llili 



iii 3 



iiili 



\imm 



aiiiiiii 



iiiiiiii' 



m 



m 



i 



11 



i 



II 



tiiK 



! ii 



ij 



i 



i 



m 
m 



iii 



lii 



I 



ill lii I ;i; lii 



!l 



!i!il 



m 



il iiili 




Class "Vft v,Ail- 
Book .TJlI 



COPYRIGHT DEPOSrr. 



CRUSHED STONE AND ITS 

USES 



FACTS OF IMPORTANCE IN CONNECTION WITH 
MODERN CONCRETE CONSTRUCTION 



Compiled by W. J. Jackman. 



PUBLISHED FOR COMPLIMENTARY DISTRIBUTION BY 

THE PRODUCERS SUPPLY COMPANY 

CHICAGO, 1904 



LIBRtRY «f CONGRESS 

OCT 17 1904 
Oonyrleht Entrv 

SS 6c <^r.. No 



TABLE OF CONTENTS 




Pac;k 

Introductory 5 

Ideal Fireproof Material 7 

Lessons of Baltimore Fire 14 

Safest Form of Construction ig 

Versatility of Concrete 23 

Fireproof Stairways 26 

Concrete Sewers and Tunnels 29 

Novel Sewer at Moline, 111 32 

Concrete in Public Works 3^ 

Lincoln Park Sea-VVall 37 

Chicago's Concrete Formula 40 

Screenings for Street Paving 42 

The l^est Road ^Laterial 44 

Pvxacting Tests of Concrete 46 

Concrete in Track Fle\ation 49 

Railway Work in Concrete ; i 

Gigantic Concrete Bridge 53 

Concrete Storage Bins 55 

P^ngineering Feat in Concrete 56 

P^conomy of Concrete 57 

Advantages of Screenings 59 

Concrete Canal Locks 60 

Comparative Concrete Tests 62 

Irrigation and Power Plants 68 

Defects of Sand 70 

Rational Setting for Steel 73 

Concrete at McCormick Works 

Concrete Poundation Piers 

Superiority of Screenings 

Progress in Concrete 

Chicago's P^irst Concrete Building 

Tensile Strength of Concrete 

Economy in Street Paving 91 

Cost of Street Paving 97 

Limestone Macadam Roadways 99 

Screenings for Drainage Canal 100 

Screenings Concrete the Best 103 

Concrete Railway Ties 104 

Concrete Posts and Conduits 105 

Limestone Screenings Test 107 

Cost of Sewer Construction 109 

Table of Voids no 



74 
71 
79 
82 

85 
89 



Copyright, 1904. by the Producers Supply Co, 



^Ml^ 




INTRODUCTORY 



D 



N the compilation of this volume pains have been taken 
to obtain from reliable sources accurate information 
concerning the various uses of crushed stone that will 
be of value to everybody interested in economical and perma- 
nent works of construction. Its contents embrace the author- 
itative views of experts who have given much time and careful 
thought to a study of the subject— men of practical experience 
who hold prominent place in engineering, architectural and 
building circles. From the expressions of these experts the 
following facts of vital importance are deduced: 

First- — That concrete made with crushed limestone, 
screenings, and good cement is the ideal material for every 
conceivable form of construction in which economy and per- 
manency are desired. 

Second — That this kind ot concrete is absolutely fire- 
proof, and is the only building material which may be so 
classed. In addition to the opinions of construction experts 
this is now largely admitted by insurance men and rates are 
being readjusted on this basis. 

Third — That the substitution of limestone screenings 
for sand results in a stronger and more durable and homo- 
geneous concrete product, while at the same time the expense 
is considerably less. 

Fourth — That it is to the financial interest of taxpayers 
in municipalities like Chicago to insist upon a more general 
use of crushed stone and screenings concrete in all works of 
public improvement wherein it may be employed, such as 
sewers, street paving, curbs and gutters, sidewalks, etc. 

Fifth — That aside from the item of cheapness in first 
cost the durability of concrete insures a marked economy in 
subsequent expenditures for maintenance. 



Ample evidence as to the accuracy of these statements 
may be had in the fact that corporations and individuals 
who are expending enormous amounts of money in construc- 
tion works unhesitatingly give preference to crushed-stone 
concrete. They have large interests at stake, and as a matter 
of precaution have investigated the subject thoroughly. Their 
own statements tell the whole story — "We use crushed-stone 
concrete because it is the best, the cheapest and most durable." 
In the hope that this book, while it falls far short of 
doing full justice to the subject, will receive the impartial 
attention which the importance of the topic warrants, it is sub- 
mitted by the 

PRODUCERS SUPPLY COMPANY. 

Chicago, 1904. 



Note — Any special information which may be desired will be furnished 
promptly by the Producers Supply Co., 418 Chamber of Commerce Building, 
Chicago. 



Concrete the Ideal Fireproof IMateriaL 



BY W. P. ANDERSON^ 



(President Ferro Construction Co., Cincinnati.) 



Concrete construction is rapidly forging to the front in all parts 
of America as the coming building construction, and the reasons 
for this are manifold, chief among which are the following : 

First — Its cheapness. It is the most economical fireproof con- 
struction in existence, being cheaper than steel and hollow tile and 
-only slightly more expensive than mill construction and, in fact, in 
certain cases in factory work concrete construction can be put in 
for the same price as mill construction. 

Secondly — Its absolute fireproof properties. This feature has 
been demonstrated in a number of instances, both in actual fires 
and in test buildings which have been erected for the purpose. The 
writer does not believe in the use of cinder concrete for structural 
work, so I will not go into that branch, but confine myself to stone 
and gravel concrete and give a few examples where they have with- 
stood fire and water tests with wonderful success. 

A few years ago the Ransome Concrete Company of New York 
erected a small building at ]\Iineola, L. I., which was tested by fire 
and w^ater. The building was lo feet 6 inches wide by 14 feet, in- 
side dimensions, wath a clear height of 10 feet above the grate bars. 
Three of the walls were of concrete, consisting of two shells each 
3 inches thick separated by a 6-inch air space, but connected by 
vertical ribs of concrete 3 feet apart. The fourth wall was built of 
brick to afford a comparison between the two materials under the 
same conditions. The roof w^as constructed to correspond with the 
regular Ransome floor construction, consisting of concrete beams 
reinforced with twisted steel bars, a concrete floor slab 2 feet thick 
connecting these ribs and concrete ceilings i]^ inches thick in three 
of the bays. The rib, roof slab and ceiling were made monolithic, 
and both the roof and ceiling were strengthened with j4-ii^ch twasted 
steel bars. The concrete w^as mixed in the proportion of one part 
of Portland cement to five parts of crushed rock, taking the produce 
of the crusher from %-inch down. The building w^as allowed to 
stand until the following year, when the roof was loaded with bags 
of gravel to produce an evenly distributed load of 158 pounds per 
square foot. This load produced no measureable deflection. The 
grate bars were covered with about 6 inches of straw, over which 
was thrown old lumber of all sizes to a depth of 3 feet. To record 
the temperature of the fire a pyrometer was rented from Messrs. 
Eimer & Amend and operated by their expert, Mr. Chaddock. The 
fire was lighted at 11:40 a. m. on November 29, 1901, and in ten 
minutes the temperature reached 842 degrees F. and continued to 
rise as recorded in the table below : 




CONCRETE CONSTRUCTION IN CINCINNATI, O. 
(The lower view shows a test of a Concrete floor loaded to 320 pounds to the foot.) 



AVERAGE TEMPERATURE OF FIRE. 



Time. 


Temperature. 


Time. 


Temperature. 


11.50 A.M. 


842" 


1.50 P.M. 


1886^^ 


12.00 


14/2 


2.01 


1746 


12.10 P.M. 


1405 


2.09 


1832 


12.20 


1499 


2.20 


1967 


12.30 


1535 


2.28 


1706 


12.40 


1580 


2.40 


1868 


12.50 


1697 


2.50 


1634 


1. 00 


1715 


3.01 


1850 


1. 10 


1526 


3.10 


1697 


1.20 


1778 


3.20 


1949 


1.30 


1904 


3-31 


1814 


1.40 


I57I - 


3.3cS 


1922 



Additional lumber was thrown on the fire about every twenty 
minutes to maintain an averag^e temperature of not less than 1,700 
degrees, which is the usual practice in such tests. At 3 40 p. m., 
the fire having burned the specific four hours, the large door in 
the concrete wall was opened and a stream of water from a lyg- 
inch nozzle, under a pressure ranging from 60 to 65 pounds per 
square inch, was directed against the concrete walls and ceiling for 
five minutes. The water was pumped by a steam engine from two 
large watering carts. As the fire progressed some fine cracks ap- 
peared in the concrete walls and one large crack in the brick wall 
extending from the door to the roof. This crack may have been 
partially due to the opening of the firing door. It finally opened up 
two inches and bulged away from the roof for about four inches. 
Two other serious cracks occurred in the brick wall extending from 
the small doors across the corners of the building and producing 
the only large crack which occurred in the concrete walls. The 
three concrete walls remained absolutely true to line, and at no time 
were they so w^arm but that the hand could be held comfortably 
against them. This is also true of the roof sections having a ceil- 
ing, which proves conclusivelv the insulating qualities of the Ran- 
some double wall and floor construction. The roof deflections were 
read by a level supported on an adjacent platform. The maximum 
deflections at the center of the beams varied from i 15-100 inches 
to 2-10 inch. The force of the water where concentrated on the 
concrete ceiling i^ inches thick was sufiicient to penetrate it and 
three holes were thus made in the ceiling. The water also slightly 
washed the concrete off in other places, exposing some of the small 
bars in the ceiling, but no vital damage was done, as the ceiling 
could be readily repaired, and the strength of the roof construction 
was unimpaired, as proven by the subsequent test load. The inner 
shell of the concrete walls contained some small vertical cracks and 
was pitted in spots by the force of the water. The brick wall con- 



tainecl hair cracks running in all directions, in addition to the large 
cracks previously mentioned. 

From the standpoint of repairs the brick wall would have to 
be taken down and rebuilt, whereas the strength of the three con- 
crete walls was in no case seriously impaired. The roof had not 
been penetrated by either the fire or water and had sustained its 
safe working load without excessive deflection. The maximum de- 
flection after the test was i 2-10 inches for the section with the 




IXGALLS BUILDING. (JINCINN AH. O. 
(Constructed entirely of Concrete.) 



ceiling and 2 inches for the section without the protection afforded 
by the ceiling. The load was removed and an examination made 
some days later indicated a permanent set of only about y^ inch. 
To determine the loss of strength, if any, in the roof construction, 
due to the combined action of fire and water, a concentrated load 
was graduallv applied at the center until equivalent to a distributed 

10 



load of 1,123 pounds per square foot without producing any serious 
deflection. 

A number of tests were made over ten years ago by the fire de- 
partments of the cities of Berlin and Vienna ; more recently by the 
British Fire Prevention Committee, and later on reinforced con- 
crete floors by the Building Department in the city of New York. 
In the latter city for each test a house 10x14 feet in the clear and 
12 feet high was built and covered by a concrete floor to be tested. 
The interior of the house was filled with coal and wood, and for 
five hours a temperature of 2,000 degrees Fahrenheit was main- 
tained, and then a stream of water from the nozzle of a steam fire 
engine was directed for a few minutes on the ceiling. All the floors 
stood the test remarkably well, supporting uniformly distributed 
loads of 150 pounds per square foot without undue deflection and, 
with the exception of a few fine hair cracks, which disappeared after 
cooling off, no damage whatever was done to the floors. I w^ould 
also cite a fire test made by the Belgium government on a two-story 
pavilion erected for that purpose at Ghent, Belgium. 

While the examples above cited have been on test houses built 
for that purpose, we find that the same satisfactory results are ob- 
tained in actual fires. Examples of this kind can be found in the 
fire at the works of the Pacific Borax Co., at Bayonne, N. J., during 
the night of April 11, 1902. An account of this fire can be found in 
the Engineering Record of April 23, 1902. The portion of the plant 
that was of concrete construction went through the fire practically 
uninjured, while the annex, which was of unprotected steel con- 
struction, became a distorted mass of iron after the fire. The writer 
has a letter from Mr. Z. B. Zabriske, New York manager of the 
Pacific Coast Borax Company, in which he says, speaking of con- 
crete construction, they having decided to rebuild entirely of con- 
crete : "We are so thoroughly convinced of its proofness against 
fire that we have decided not to carry any insurance on our factory 
building or its contents." 

By far the most important fire in which concrete was demon- 
strated beyond doubt the best of fireproof constructions was that in 
Baltimore in February, 1904. We can mention among the con- 
crete buildings which withstood that fire, Junkers' hotel and the 
International Bank building, built entirely of reinforced concrete. 
The columns, girders and floors of these buildings remained intact, 
although their contents were entirely consumed. We also can call 
attention to the United States Fidelity & Guarantee building, which 
was in excellent condition, although all other buildings in the block 
were entirely consumed (see Baltimore American, Jan. 21, 1904; 
also Cement, ]\[arch, 1904; also the Chicago Daily Tribune, page 5, 
Feb. 13, 1904). 

At the present time the insurance rates on concrete construction 
are as low as on any other form of construction in existence, and it 
is my firm belief that in a few years they will undoubtedly be lower. 
I here give a table taken from the July, 1902, number of ''Ce- 
ment" (Progress Publishing Co., 13 Park Row, New York, N. Y.). 



This shows the wonderful strength of concrete and also the great 
increase in strength with age. The results given are based on con- 
crete made of Portland cement, clean sharp sand, with 33 per cent 
voids loose and broken stone. Cement and sand turned twice. Mor- 
tar and stone turned twice. 



MIXTURE. 


Weig 


ht Resistance in Pounds. 












VJ 


<A 


c 
S 


'6 

a 




>. 




C 






u 


CT} 


C/3 


r^ 


T— 1 


m 


VO 




I 


1 

3 ' 


1600 


2750 


3360 


4300 




2 


4 


1400 


2400 


2900 


3700 




2)^ 


5 


1300 


2225 


2670 


3400 




3 


6 


1200 


2ot;o 


2440 


3100 




3y2 


7 


I 100 


1875 


2210 


2800 




4 


8 ' 


1000 


1700 


1980 


2500 




5 


10 1 


800 


1350 


1520 


1900 




6 


12 1 


600 


1000 


1060 1 1300 




IDEAL FACTORY COXSTRUCTIOX IX COXCRETE. 

On page 1,102 of Reports of Tests on [Metals and Other Ma- 
terials for Industrial Purposes, published by the Government Print- 
ing Office, Washington, D. C, for the year 1900, it will be seen 
that a test on concrete made on a one part Portland cement, two 
parts lake sand and four parts broken limestone showed an ultimate 
strength of 3,520 pounds per square inch. 

While concrete construction has made rapid advances through all 



12 



portions of the United States in the last few years, Cincinnati has 
probably taken the lead in this particular. The Ferro-Concrete 
Construction Company of that city has erected a number of build- 
ings there in the last few years, the most notable of which is the 
Ingalls building at the corner of Fourth and Vine streets. The first 
three stories were veneered with marble. Above the marble the 
building was veneered with enameled brick. This building is 210 
feet high above the ground, having sixteen stories. It is the high- 
est building of concrete construction in the world, absolutely no 
structural steel having been used in any portion. The stairs, pris- 
matic lights, and in fact the entire building is of concrete. The 
Ingalls Realty Company are the owners of this building, and Elzner 
& Anderson of Cincinnati were the architects, and they, together 
with the Ferro-Concrete Construction Company, deserve a great 
deal of credit for the faith that they showed in undertaking this 
work. The results have been extremely satisfactory, no defects of 
any kind having been discovered in the building. In fact, it is 
such a success that a number of other owners have adopted con- 
crete construction for their buildings in Cincinnati, among which 
may be mentioned the following, w^hich are being erected by the 
Ferro-Concrete Construction Company : 

A large factory and office building for the American Book Com- 
pany, covering one-half a block of ground at Third and Pike streets, 
Cincinnati. A seven-story building for Mr. Louis J. Hauck at Sev- 
enth and Main streets, Cincinnati. A branch bank for the Union 
Savings Bank & Trust Company at Twelfth and Vine streets, Cin- 
cinnati. A telephone exchange for the Citizens' Telephone Com- 
pany, Covington, Ky. 

Following the success of the Ferro-Concrete Construction Com- 
pany other contractors have taken up the business in Cincinnati 
and are at work on the following concrete buildings : A large fac- 
tory for the A. H. Pugh Printing Company, Fourth and Pik'fe 
streets, and a six-story building for the John Van Range Company 
at Fifth and Broadway. The grand stand for the Cincinnati ball 
park is' also entirely of concrete construction. 

One of the important uses of concrete construction is for fire- 
proof vault work. Such a vault has been put up for the First 
struction, showing the outer form work up on two sides and the 
steel reinforcement in position. The thickness of the concrete w^alls 
in this instance is 6 inches. The vault was put up for the First 
National bank of Norwood, Ohio. Similar vaults have also been 
built for the Union Savings Bank & Trust Company and the Mer- 
chants' National bank. 

One of the floors at the American Book Company building was 
slightly frozen and the owners wished to have it tested thoroughly 
on that account. The floor w^as figured to carry 200 pounds, b'ut 
was loaded to 320 pounds with dry sand weighing about 90 pounds 
to the cubic foot. The portion loaded was 68 feet by 171^ feet. 
The test was entirely successful and was more severe than any load 
the floor could get in ordinary use, especially as it was impossible 
for the sand to arch. 

13 



Object Lessons of the Baltimore Fire. 



(Extracts from the Official Report of the Insurance Experiment Station at Boston, Mass,^ 

This great practical test by the ] Baltimore fire has sustained several 
concUisions that had been indicated in other fires of less magnitude 
and by our laboratory tests of materials and processes. Granite again 
proved to be the most unfit. This conclusion had long since been 
reached from the results of the conflagration in Boston. On wit- 
nessing that all the granite exposed had been reduced to sand, I 
asked an explanation of the late President \\'illiam B. Rogers, who 
told me that granite was more or less porous, all varieties containing 
sufficient water in hygroscopic form to make steam under heat, which 
rends the rock into sand. Granite is also a crystalline conglomerate 
which splits or spalls under heat because of the stress set up bv its 
unecpial expansion in different parts and in different directions. 

The relative fire resistance of building materials of an artificial 
character was thoroughly tested. Terra-cotta has failed. We had 
been led to expect such failure from the condition in which large 
buildings had been left after serious interior fire, but these cases had 
not been sufficient to establish a rule, in this cc^nfiagration the rule 
seems to be established. 'Vhv faihuT to resist high temiKTature is 
due both to the quality of the material itself which is more or less 
subject to disintegration under heat, and to its exi)ansion. The 
greater fault is that terra-cotta lilocks. ])lates, and other forms are 
detached by expansion in large masses from the ste^el. This is due 
to the fact that terra-cotta and steel ex])an(l and contract under heat 
in sufficiently dift'erent ratios to reiifler such encasement or ])rotection 
of little service. The ])hotogra])hs of the conditions under which 
terra-cotta parted from the steel or was practically destroyed, sus- 
tain this view, while the laboratory tests and exact measurements 
made by Professor Norton give the rule of relative exi)ansi()n and 
contraction. 

\\>11 made concrete encasing steel ])roves to be most fully a fire 
resistant when it is made with true Portland cement rammed and 
tamped in a proper manner. It fortunately happens that a well 
made concrete of this kind is subject to a law of expansion and con- 
traction under heat so nearly identical with that of steel as to 
assure its position being maintained under high and varying tem- 
peratures. 

When large city buildings are planned with the slightest con- 
sideration to their own safety from internal hazard and with full con- 
sideration of the danger of the neighborhood, they may not only 
be made safe in themselves, but may be made the standing places 
for resisting the spread of conflagrations around them in the most 
effectual manner; and when steel frames are inbedded in Portland 
cement concrete that will not only resist fire but prevent corrosion, 
they may become permanent safeguards in every city where many 
of them now constitute a constant menace. A conflagration in 

14 



Baltimore or elsewhere had long been forseen ; plans, estimates and 
methods of meeting this hazard were prepared by the undersigned 
and his associates in 1884. The calamity in the Iroquois theatre was 
foreseen, and right methods of providing against it were also printed 
in detail in these documents, which then and since have had a wide 
circulation. It, however, seems to require a Chicago calamity and 
a Baltimore conflagration to force the attention of citizens and of 
the authorities to take the simple, plain and adequate measures for 
the prevention of these disasters. Respectfully submitted, 

EDWARD ATKINSON, Director. 



I visited Baltimore five days after the beginning of the fire and 
spent three days in looking over the field in a general way, interview- 
ing eye-witnesses and making a rather limited examination of the 
ruins largely from the streets. Ten days later I made a second visit 
of four days, spending the time almost wholly in studying the condi- 
tion of the so-called fire-proof buildings, examining them all except 
the Herald building. The details of the fire and the general descrip- 
tion of the condition of the district after the fire, have been so thor- 
oughly published as to call for no further repetition here, and it is 
my purpose to call attention only to the more technical lessons to be 
learned from this conflagration. 

The steel posts and beams in about all the buildings were cov- 
ered either with terra-cotta or with "lime-teil," a material whose 
composition appears to be in the nature of a plaster and cinder mix- 
ture. Generally the covering was destroyed or badly damaged, A 
very large percentage of the terra-cotta and lime-teil block must be 
replaced, and it is the general, almost universal, condition that the 
beam covering of the flanges is gone. The loss of terra-cotta beam 
and post coverings was at least 75 per cent. The partitions of terra- 
cotta and lime-teil are very largely destroyed and the unfitness of 
these materials for this purpose seems clear. Many partitions have 
fallen and more are in such condition that they must be replaced. 
Much of the lime-teil is softened and the terra-cotta is cracked or 
broken and the bond between blocks is loosened. If metal lath parti- 
tions wTre in existence to any great extent, they failed as well, for few 
were in evidence in good order. The floor arches of many different 
spans and of different details of construction, but in the main of 
terra-cotta or lime-teil, show much the same sort of distress as the 
partitions. The bond between the tiles is broken, quite generally, and 
the tiles themselves are cracked and broken in great numbers. The 
lower face or soffit of the tiles has split oft' over large areas, and 50 
or 60 per cent of the terra-cotta floor construction will, I fear, need 
to be replaced or reinforced. 

Where concrete floor arches and concrete-steel construction re- 
ceived the full force of the fire it appears to have stood well, distinct- 
W better than the terra-cotta. The reasons I believe are these — 
first: because the concrete and steel expand at sensibly the same 
rate and hence when heated do not subject one another to stress, but 

15 



Concrete-encased Steel Pilla 
uninjured by intense lieat. 




International Trust Buildiu}^ of 
Concrete and Steel Construction. 



OBJECT LESSONS OF THE BALTIMORE FIRE. 



terra-cotta usually expands about twice as fast with increase in tem- 
perature as steel, and hence the partitions and floor arches soon be- 
come too large to be contained by the steel members which under 
ordinary temperature properly enclose them. Under this condition 
the partition must buckle and the segmental arches must lift and 
break the bonds, crushmg at the same time the lower surface mem- 
ber of the tiles. Especially in the Calvert Building I found evidence 
which leads me to believe that not an excessive temperature, but the 
differential expansion under a moderate high temperature of the 
terra-cotta of the top and bottom members and of the enclosing steel, 
is responsible for the general failure of the terra-cotta partitions, 
beam-covering, and floor arches. Secondly: IMr. Gray suggests 
that there is a similar unequal expansion of the top and bottom 
faces of the separate tiles, which causes the lower faces to expand 
and shear off. Evidences of this were found everywhere. 

Further examination of the expansion phenomena points to them 
as the main source of distress to the whole beam and post covering, 
floor arches, and partitions. Most of the fallen terra-cotta partitions 
and the floor blocks were still hard and had a clear ring when 
struck, thoug-h cracked and broken. There was no- evidence of any 
such temperature as that at which the terra-cotta had been baked 
originally, and the material of the blocks could not have been al- 
tered chemically. It w^ill be readily understood that the thin walled 
hollow tiles would become heated upon one side much more quickly 
than would the equivalent area of a solid partition of brick or con- 
crete. The minor details of the structure and finish fared badly. 
Wood is not in evidence except in secluded corners. Marble, slate, 
plaster, and in fact all similar surfacing material suffered to the 
point of destruction. 

The building of the United States Fidelity and Guarantee Com- 
pany is an interesting example of reinforced concrete in the district. 
As near as I could ascertain, it was subjected to a severe fire and I 
found evidence of temperatures up to the softening point of cast iron. 
The condition of the lower part of the structure and of apparently 
of the whole structure showed the great fire-resisting powers of this 
type of building. It is of especial interest in that the Experiment 
Station made a preliminary test on an arch of this same type and 
of almost this exact thickness and span and weight of metal, which 
failed because of the slender six-inch posts, and not through the 
failure of the floor, at the end of three hours and forty minutes' 
exposure to a 1700 to 2000 degrees Fahrenheit fire. 

Further, in the International Trust Company Building a small 
paper room having a Hennibique (concrete) floor and ceiling, was 
so intensely heated that at the end of three days the lumps of cast 
iron which had earlier been a copying press and an embossing stamp 
were still red hot, and yet neither floor nor ceiling showed signs of 
distress. This is the more remarkable in that the walls of the ad- 
joining building fell through the skylight upon the Hennibique 
floor. There were in the Commercial and Farmers National Bank 



and in the National Bank of Commerce concrete floors which stood 
the fire test well. 

The general condition of the fire-proof buildino- is snch as to 
indicate to my mind the nnfitness of terra-cotta for beam and post 
covering and floor construction as here used when compared with 
concrete. Second, there is no evidence that the tall steel build- 
ing was subjected to an unusually severe test. While it must be 
admitted that no encugh concrete received the full effect of the 
fire to make the test a perfectly complete one, when I add to 
this the experience of several years in examining the action of fire 
upon concrete, I am convinced that had the floors of the Continental 
Trust or the Calvert Building been of any one of the better class of 
concrete types and had the beams and posts been encased in four- 
inch coatings of sound concrete, their renewal would have required 
little but plastering-. 




COXCRKIE FOLN TAIN AT KLCilN IIJ.. 

Much has been said about the uncertainty of concrete. The 
value of concrete in theory is often admitted by those who consider 
it unwise to use it because of the difficulty of getting the materials 
properly proportioned, ir.ixed, and placed in position. I have never 
been able to see the force of this. It is quite as easy to lay sound 
concrete as it is to put somewhat irregular and confessedly brittle 
blocks of terra-cotta into place with proper bonding. It seems ap- 
parent that, with care, steel frame buildings can be so constructed 
as to stand the destruction of their contents without injury to the 
steel and probably without danger to the protecting material or floor 
arches ; that, with shutters and wired glass, the burning of more 
combustible neighlx)rs may be expected to cause little permanent 
injury to the structure proper; and that a district composed wholly 
of such buildings would be reasonably immune from danger of 
conflagration. 

18 



C. L. XORTON. 



On the week following the fire I visited Baltimore and spent 
ihe greater part of two days' time in examining the result of the fire 
on the different t\pes of construction and studying its effects, as 
far as it was possible for me to do in that length of time. My con- 
clusions are similar to those of Professor Norton's and with some 
slight variations, which would not affect the main body of the re- 
port, I heartily approve of the same. I especially approve of that 
part of the report relating to the advantages of concrete construc- 
tion, basing my opinion on observations made not only at this lire, 
but at previous ones which haye occurred in buildings of concrete 
and other types of so-called "fire-proof" construction. 

J. P. GRAY, C. E. 

Concrete the Safest Form of Construction. 



BY GEORGE WILLIAMS, 
(Commissioner of Buildings for the City of Chicago.) 

It would not be proper for a building commissioner to publicly 
say anything which could be construed to favor any one kind of 
construction material to the exclusion of others, but it is very nat- 
ural for a person to form opinions on this subject, especially when 
the work is before him every day and he can see the results in all 
stages. Facts are facts, and we cannot get away from them. Just 
now the topic of fireproofing is attracting wide attention. The re- 
cent disaster in Baltimore will be fruitful of gigantic strides in the 
art of fireproof construction, and it is a matter of prime interest 
to everybody, directly or indirectly. In all the reports thus far 
received from Baltimore concrete is given the highest praise as 
having withstood the most crucial of fire tests. This, in my opinion, 
will be the cause of radical advances in the construction of really 
fireproof buildings. Many prominent architects have made 
inaking the most exhaustive studies of the effects of the fire on con- 
crete and steel, and from their deductions will be evolved structures 
of the desired qualities. Such reports as I have read from these 
sources convince me that the combination of concrete and steel 
makes the most nearly actual fireproof construction it is possible to 
secure. Hollow brick also stood the test, but concrete was fully 
equal to it when built solidly about the steel pillars. 

As an example of the fire-resisting qualities of concrete I would 
point to the Iroquois theater, in this city, which burned on December 
30th last. The floors in that building were all made of crushed 
stone concrete, and on the lower story were suspended in 16-foot 
spans. While the intense heat caused the brick walls to crumble on 
the side exposed to the flames in a remarkable short time, the con- 
crete floors never budged, and are as solid to-day as when they 
were first put in, although tons of iron and other debris fell upon 
them, and the wooden strips were burned out. These floors not 
only stood the test of heat and unusual weight, but when an im- 
mense volume of steam was formed bv the water from the fire en- 



gines being poured upon the flames not a single crack, not a warp 
or a bulge in the entire surface resulted. This floor construction 
was of varying thickness, running, I believe, from about 5 to 8 
inches. The steel pillars supporting the galleries and balcony were 
fireproofed with concrete, and not one of them was in the slightest 
degree affected, despite the fact that the heat was of an unusually 
intense nature. 

On the other hand, at the recent fire in the ]\lasonic Temple 
the tile fireproofing crumbled soon after the heat struck it, and 
when the water was turned on it fell from the walls and ceilings. 
The combination of heat and water destroyed it completely. 

These two instances will serve as an illustration of what "fire- 
proofing" really is. If anybody wishes to get an accurate idea of 
the amount of intense heat good concrete will withstand he will 
find no better evidence than right here in Chicago at the Iroquois 
theater. There is one concrete armored ^rirder to which I would 




COXCRKIK PR0SCP:XIUM .arch. IROQUOIS THEATKR, CHICAGO. 
I'MXIIRKI) BY THF. FIRK. 

call special attention. This is the girder over the proscenium arch, 
where all the mass of flame which destroyed the interior of the 
theater hung. This concrete was subjected to a heat which was 
more severe than can be estimated, still the steel in the girder back 
of the six inches of concrete was not affected in the least. The 
concrete and plaster about the columns in the auditorium abso- 
lutely protected the steel in them. From observations made the day 
after the fire I found that the actual fireproofing work in the theater 
was perfect, and that not a single piece of the steel thus protected 
was aft'ected in any way by the intense heat of the fire. 

Our city building laws do not, and cannot, specifically provide 
for the use of concrete as against other materials, for this would 
be discrimination, and there are as yet many believers in other 
kinds of construction. But the laws are in such shape that the use 
of concrete is encouraged wherever it is possible to do so. So far 
as the city departments themselves are concerned there has been 

20 



little concrete work done. Its use has been confined to two sewers, 
bridge abutments, pumping stations, street paving and sidewalks. 
Otherwise the employment of concrete has been thus far neglected. 
But this condition will exist for only a short time. Our city experts 
have been experimenting with various materials with the purpose 
of the general introduction of concrete in the construction of all 
public works, and it may as well be known that the product of 
crushed limestone has found most favor as being best adapted to a 
wide range of work. The reasons they advance for holding to 
this opinion are, first, that the sharp and jagged edges of the 
limestone make a better surface for the concrete to bind upon than 
the round, polished pebbles and stones in gravel ; second, that the 
porous nature of the limestone permits the moistened cement to 
permeate it and thus force the cement into the stone. But to my 
mind the principal thing is in the making. If the voids are filled in 
the use of either material the mass of concrete will harden until it 
is like granite. Cement, with screenings or sand, will fill the voids 
and make a compact and homogeneous mass. It would appear to 
me that the limestone concrete is a more logical and homogeneous 
body than a mixture of gravel and cement. Cinders as a basis for 
concrete I do not think much of, but considerable quantities of them 
are used. I would prefer crushed stone of smiall dimensions. It 
has the body which is lacking in cinders, and the use of the latter 
is permissible only where it is essential to obtain the advantage of 
light weight. 

Concrete work is yet in its swaddling clothes in this city, or in 
the United States for that matter. In Germany, and in other foreign 
countries, it is full grown. But while still of tender age here, it is 
growing rapidly, as the following figures will show : Ten years ago 
the annual consumption of cement was about 5,000,000 barrels. 
Last year it reached something like 30,000,000 barrels. This is a 
gain of about 600 per cent., and I believe that within the next ten 
years the annual consumption w^ill reach somewhere between the 
60,000,000 and 100,000,000 barrel marks. The use of cement in 
concrete work represents about one-fifth of the total amount of 
concrete. This is probably a little under the actual figures, but it is 
employed in something like this proportion in the making of all 
concrete. This would make the volume of concrete work (an- 
nually) about 80,000,000 yards. These figures are general, but they 
illustrate the progress in this phase of construction throughout the 
country. Chicago is moving as rapidly in this respect as any city, 
and perhaps a little more so, as concrete has come to be a dominant 
factor in building of all kinds here. 

But it is in the erection of buildings that the most rapid ad- 
vancement is being made in Chicago. From the sub-structure of 
piles to the floating foundations of railway iron and concrete, and 
then to solid pillars of concrete running down to hardpan or solid 
rock, this interesting phase of building construction has developed. 
As a foundation for immense structures concrete used in the form 
of pillars has been proven far superior to anything known to modern 



builders. Next came the development of the concrete as a valuable 
material in walls and floors in the superstructure. Its strength and 
fireproof qualities are now recognized by progressive builders and 
architects, and, taking advantage of the experiments in this line 
made in foreign countries, its use by many of our leading firms of 
architects has become general. 

One Chicago structure which has been watched with great 
interest is the new Railway Exchange Building, where con- 
crete was used in every possible nook and corner. It is the 
almost unanimous opinion among experts that this building fur- 
nishes a perfect specimen of actual fireproof construction. All 
the columns are fireproofed in a novel manner. A brick covering 
was erected four or five inches from the steel column and the space 
filled with concrete, thus making the column of double sustaining 
power — adding that of the concrete to the steel — and at the same 
time effectively fireproofing the steel. Where pipes and flues are 




COXCRETl:: WORK IN IROOl'OIS THEATER ININU'RED 
BY TH1-: 1-IRE. 

built the brickwork surrounds the aggregation and the concrete is 
tamped down between each pipe, making the column a solid pillar, 
as it were, and at the same time leaving the flues and holes as per- 
fect as if each were hewn through solid rock. In the construction 
of concrete floors, which are now quite common in Chicago, the 
i6-foot span is considered ample to sustain any weight which may 
be placed on the floor. The spans are reinforced with steel or iron 
bands and the floor is thus made as rigid and unyielding as it is 
possible to do. 

All this, we must remember, is in the infancy of concrete. Up 
to three or four years ago it was practically impossible for the 
advocates of concrete construction to get a hearing from archi- 
tects. I know of one man who tried very hard and persistently, but 
without success, to get the subject before a certain firm of archi- 
tects, being turned down with a curt note of declination. This 



same firm is now doing the most elaborate work of concrete con- 
struction in the West, and has gone into the business on an im- 
mense scale. This incident is cited only to show the tendency of 
the times. It illustrates my assertion that in a comparatively short 
time Chicago will be a city of concrete buildings. It is- strange to 
me that this condition does not already exist, when such smaller 
cities as Columbus and Cincinnati and Philadelphia have made such 
wonderful progress in this line. 



Versatility of Concrete as a Construction Material. 



BY V. W. ALLING, 
(Construction Expert for Wells Brothers, Building Contractors.) 

Just after the construction of the new Belvedere hotel in Balti- 
more, a test of the fire-proofing occurred which was not 
on the programme. It was an accidental blaze, but it served 
the purpose of demonstrating that the concrete work in the 
building could stand intense heat without disintegrating. 
This impromptu test cost about $2,000 in the furniture 
destroyed, but it was worth fully that and more. It explains why 
the Belvedere hotel stands today in that city of ruins, surrounded 
on every side by the wrecks and debris of other misnamed "fire- 
proof" buildings. 

The Belvedere was put up by Wells Brothers of Chicago and is 
a model in steel and concrete construction. Crushed stone played 
an important part in its erection. Something like 7,000 yards of 
this material were used. The foundations are of crushed stone 
concrete, built from the rock to the steel floor beams. This work 
is similar to that now in general use as regards the mixture and 
method of placing. Every one of the twelve main floors are mad*e 
of crushed stone concrete, and are built in spans 16 by 8 feet. Mos't 
of them are of a thickness of 6 inches, those on the lower stories 
being a little heavier. The work of construction was of the rapid 
order. It was started on January 6, 1903, and on Christmas day 
of the same year the hotel was formally dedicated. On November 
12, just after the building was virtually completed, a fire occurred 
in rooms 188 and 189, on the sixth floor, where a large amount of 
furniture had been stored. This fire burned for thirty minutes or 
more and was very hot, being fed by the varnished and painted fur- 
niture and the inflammable excelsior packing. The door between 
the two rooms was open and the fire extended to both of them. 
When the blaze was extinguished it was found that the papering 
and decorations on the walls in the rooms next to those where the 
fire took place were not in the least disturbed or damaged, and no 
repairs were necessary. More surprising even is the well-estab- 
lished fact that even when the fire was raging the walls in the ad- 
joining rooms were cool and gave no indication of the intense heat 
on the other side of them. The fire was confined to the apartments 

23 




BELVEDERE HOTEL. BALTIMORE, MD.. THE INTERIOR CONSTRUCTION 
OF WHICH IS ALMOST ENTIRELY OF CONCRETE. 



in which it started, and the absolute fireproof character of the 
structure was thus proven. Concrete fireproofing covers the metal 
lathing in the walls between all rooms and in all partitions, while 
the window sills and casings are of metal. These concrete walls 
are so compactly and thoroughly built that even the smell of smoke, 
which almost invariably permeates a building in an affair of this 
kind, could not be detected in the rooms next to those where the 
fire occurred. In commenting upon the incident Mr. Emerich, act- 
ing chief of the Baltimore fire department, said : 

"The blaze was an adequate test of the fireproof qualities of the 
new building. When the seat of a fire in a structure of this char- 
acter is reached there is little difficulty in subduing it. The flames 
had made good headway when the firemen got to work, but the in- 
terior of the rooms was only slightly singed." 

The Belvedere stands as a monument to the value of 
crushed limestone concrete foundations, floors and walls 
in the securing of real fireproof qualities. Owing to local 
conditions we were compelled to make use of several varieties 
of limestone in mixing the concrete, but they all stood the supreme 
test satisfactorily. The entire building is of an advanced type of 
construction. On all four sides concrete is employed and all parts 
ordinarily made of wood are of metal or composition. The upper 
work is an especially exemplary specimen of what may be accom- 
plished in this line. In considering the problem of fireproofing the 
steel, at the same time having in mind the solidity of the building, 
the fact that surrounding the pillars with concrete would not alone 
fireproof them but add a double factor in weight-sustaining power 
was accepted. 

Our largest piece of concrete work in Chicago, and probably the 
most massive of its kind in the city, is at Twenty-second street and 
the river — a new power plant for the Commonwealth Electric Com- 
pany. Here fourteen concrete piers were constructed to serve as 
bases for the turbine engines. The technical difficulties encountered 
were the inertia of the machinery and the jar and vibration, which 
will be constant. For many years these huge generators must 
pound and grind. The problem was to secure foundations which 
would not give way, nor be affected in any manner by the severe 
and unusual strain. It was decided that concrete was the only ma- 
terial we could rely upon. This concrete was made with crushed 
stone, about 8,0(X) yards of limestone being used for the fourteen 
piers and for the foundations of the monster power house. Abso- 
lute solidity was an important essential in this work, and limestone 
was selected because tests have shown that it forms a homogeneous 
mass more readily than other material, and will harden into a com- 
pact and flawless base. In beginning this work piling was driven 
to the bedrock. On top of the- ^ piles the concrete was laid, cap- 
ping the timbers and forming a base for the piers. This concrete 
was of the usual mixture — one part of cement, two of sand and six 
of stone. It was thoroughly tamped and all voids entirely done 
away with. Each pier is i6 feet in diameter and some of them are 



set as deep as 30 feet. The pressure they will withstand is in the 
neighborhood of 50,000 pounds to the square foot, although in this 
instance the direct weight is not all that must be overcome — the 
terrific strain incident to the movement of the heavy generators 
must be taken into consideration. These generators each weigh 
about 300,000 pounds and are tied down with iron rods which are 
strung clear to the bottom of the pillars. The horse-power to be 
generated is 140,000, and as the machines are of the turbine variety 
we were compelled to make calculation for a much greater inertia 
than in the usual run of power machinery. 

In addition to these bases a concrete bed of simpler character 
has been made to support the sixty-four large boilers which will 
furnish the steam for the generators. This bed is about 13 feet 
wide and extends the entire length of one side of the building, about 
240 feet. It is constructed upon a foundation of piling, but is not 
laid so deeply as the concrete for the generator bases, as the condi- 
tions do not demand it. 

Concrete was em])loyed in this work, as well as in the construc- 
tion of the Belvedere hotel and in other instances, because it has 
proven to be the only material which will stand indefinitely the 
strain and wear, remain unaft'ected by weather conditions, furnisli 
absolute fireproof protection and grow better with age. In such a 
work as the Commonwealth Electric Company's power house, for 
example, natural stone would not answer, as it would have to be 
laid in blocks, and there would be the constant tendency to slip 
loose under the movement of the giant generators, while the con- 
crete body, when once set, is a solid, compact mass. Results with 
crushed limestone in Chicago have been the best that could be ob- 
tained. In both the large pieces of work which I have here cited 
this crushed limestone has been used as the basis for the concrete, 
all the materials being carefully selected and mixed under close in- 
spection. The results in all work of this nature depend entirely 
upon having a perfect concrete, and this in turn depends upon the 
care and diligence exercised in selecting and mixing the ingredi- 
ents. 

While there are other large and interesting works to which I 
could refer as establishing the merits of concrete, the two men- 
tioned are sufficient examples as illustrating two widely different 
but very important and vital qualities. Concrete exemplifies the 
material which will adequately withstand immense pressure and 
intense heat and sustain itself in an extensive area with only its 
own composition to support it. 



Fireproof Stairways IMade with Concrete. 

BY CHARLES S. FOX, 
(Engineer for Holabird & Roche, Architects, Chicago.) 

The basic principles involved in the construction of the con- 
crete stairway, which is now rapidly coming into general use, are 

26 



ancient, and the application, while of comparative recent date here,, 
as far as its use abroad is concerned ante-dates the armored con- 
crete construction which is now attracting such universal attention. 
The especial values of the concrete stairway are in its durability, 
its economy, the ease and simplicity with which it is made, handled 
and put in place, and above all its fireproof qualities, the lack of 
which in the ordinary type of stairway construction were thoroughly 
demonstrated in the big fire in Baltimore last winter, and in 
a number of minor conflagrations as well. 

The self-supporting concrete stairway of today is an amplifica- 




SELF-SUPPORTIXG, FIREPROOF STAIRWAY OF CONCRETE. 

tion of models which may yet be found in natural stone in many of 
the famous old castles and strongholds in European countries, the 
only real difference being that concrete is substituted for the stone. 
This form of stairway is built upon an arch formation, the triangu- 
lar concrete pieces being niched so as to sustain the weight of the 
stair above, and when the run is complete the arch is finished. In 
this construction no reinforcements or supports are needed other 
than the supporting wall into which the ends of the steps are built. 
For concrete stairways it is necessary to provide for the supports in 
the wall construction, which is a very simple matter if looked afte^" 



when the plans are drawn. The material may be solid concrete 
or the hollow variety, with a slight steel reinforcement if desired. 
Crushed stone concrete is used for the s-tair steps, the finish being 
had with a chipped marble composition highly polished. Each 
step is made and finished in the shop and delivered at the building 
ready to be put in place in the stairway. 

Another form of concrete stairway is built on the semi-structural 
plan. In this the treads are extended so as to s-upport the step 
above, an angle iron joining the two firmly. Although built of 
the same material and in the same manner as resrards moulding 



this stairwav is of a radically 



different design from that of the self- 
supporting kind. The ordi- 
nary stair construction is 
either of iron or iron and 
marble. In the latter the 
marble tread rests upon an 
iron riser, the whole being 
held bv iron face and wall 



Many large buildings in 
Chicago will no doubt be 
equipped with these concrete 
stairs in the future, as their 
\aluable points are brought 
out by construction and use. 
If this \-alue had been thor- 
oughly understood a short 
lime ago as it is now, con- 
crete stairways would have 
been placed in the newAdams 
building, which this firm is 
erecting at State and Adams 
streets, but the work on the 
structure has now progressed 
to a stage which makes a 
change in plans inexpedient. 
A very good specimen of the 
semi-structural concrete stairway, however, may be seen at the 
Alexian Brothers' hospital at Belden and Racine avenues. 

In a number of recent fires it has been the almost universal ex- 
perience that iron stairways collapse and give out altogether, while 
those made of concrete have shown remarkable heat-resisting 
power. There is no question about the strength or durability of 
this kind of construction. \Miile it is generally argued that stair- 
ways are of little real use as a means of escape during the actual 
progress of a fire because the flames usually close these means of 
exit" at the start, we must not lose sight of the fact that it is a valua- 
ble thing to have a building constructed in such a manner that it 
may be put into repair after a fire with the smallest possible loss of 
time and money, and this may be accomplished by the substitution 
of concrete stairways for those of other materials. It is this con- 

28 





y 



FIREPROOF. SELF-SUSTAIXIXG STAIRS. 
BUILT ENTIRELY OF CONCRETE. 



elusion, mainly, that will bring this form of concrete construction 
into popularity in the near future, as it seems everywhere to be 
giving satisfactory results. 

Leaving out the one item of concrete stairways, for the reason 
already stated, the new Adams building will afford a fine example 
of modern concrete work. Caissons, on which the fifty-four sus- 
taining columns are supported, were sunk to bed-rock, a distance 
of about lOO feet. These piers are made of crushed stone concrete 
laid by the chute plan and range from five to eight feet in diameter. 
They are all of perfect cylindrical form, with no spreading at the 
bottom, and sustain an approximate weight of twenty tons or 40,000 
pounds to each square foot. The curb and retaining walls, which 
are on the four sides of the structure and begin at a point thirty 
feet below the first floor, extending down to the sub-basement, are 
also of crushed stone concrete. The proportions of the concrete 
mixtures used in this work were varied slightly for different loca- 
tions, depending upon the load which the finished work would re- 
ceive. The general mixture used consisted of one part Portland 
cement, three parts sand and five parts of crushed stone. 



Concrete Sewers and Tunnels the Best. 



BY GEORGE W. JACKSON. 
(Chief Engineer of the Illinois Tunnel Co.) 

^1^^ One of the first works in which I 

^^^^^ employed crushed-stone concrete on 

^^^^^^^^ an unusually large scale was in the 

^W|^^^^p construction of a sewer at Reading, 

^^^ lir Pa. This work, which was under- 

*" taken to relieve the city of the flood 

waters from the Snow mountains, 
which at certain times of the year 
virtually submerged it, is about 2^ 
miles in length. The use of crushed 
stone was in a manner forced upon 
us as a measure of economy. Owing 
to the difficulty of obtaining other 
George w. Jackson, suitable _ materials I adopted the 

Engineer-in-Chief, 111. Tunnel Co. stone, with the result of an ultimate 

saving of ^40,000 in the expense of 
construction. This in itself was an important item, but it was 
overshadowed by the fact that wC'builded better than we knew." 
That sevver at Reading is to-day a model of its kind. It was built 
in 1894, just ten years ago, and has had a number of severe tests, 
but is without a flaw or defect of any nature. If I had similar 
sewer construction to do now I would not hesitate in the choice 

29 




False work before Concrete was 
put in place. 




Cross Section showing Con 
Crete work. 



SECTIONS OF THE ILLINOIS TUNNEL CO.S SUBWAY UNDER THE 
BUSINESS DISTRICT OF CHICAGO. 



of materials. Crushed-stone concrete would be given decided 
preference. 

As to the use of screenings in concrete in place of sand I will 
sa}^ that the advisibility of this depends almost entirely upon the 
character of the sand. If forced to choose between the ordinary 
run of pit sand and screenings I would select the latter every time, 
and particularly for work of my own, or in that in which I was 
free to pick my ow'n materials. The main reason for this is that it 
is practically impossible to detect imperfections or foreign substances 
in pit sand and the solidity or integrity of your concrete mixture is 
thus in doubt. On the other hand the manner in which screen- 
ings are produced precludes the admixture of any dangerous quan- 
tity of foreign matter, and if such does exist the color of the screen- 
ings makes it readily distinguishable, whereas in the sand it is hid- 
den, and difficult to detect. There can be no question as to the 
value of concrete made wdth clean screenings. 

Crushed-stone concrete has been largely used in the construction 
of the Illinois Tunnel Company's subways under the streets in the 
business section of Chicago. This is one of the largest works of 
its kind ever undertaken, and I am proud to be able to say that it 
is in every way a model of perfection. This subway is located far 
below city datura, and in a soil notoriously susceptible tO' seepage, 
but it is wdthout a trace of moisture on the interior, and has a 
w^eight-resisting power which is unequalled by any structure of its 
kind and size. For months before the actual work of construction 
was begun we made tests of every conceivable nature with crushed- 
stone concrete. The records of these I have destroyed and the 
exact figures of weight and moisture resistance, etc., have slipped 
from my mind. The weight resistance, however, I happen to re- 
member is without limit. As I now recall it one of our tests of a 
concrete made of 4 parts of crushed stone and screenings to i of 
cement, w^as totally unaffected by pressure. In other words we 
could not get w^eight enough on the cube to deflect or disintegrate 
it. This formula is the one which has been most generally used 
in our tunnel work. 

The manner of construction employed in the excavation and 
lining of this subway, wdiile highly original, has been told and retold 
so often that it is now an old story. I would say in this connection, 
however, that a w^ork of this nature would have been practically im- 
possible in Chicago without the use of concrete. It has enabled 
us to make the subw-ay one continuous pipe as it w^ere, without 
breaks or joints of any kind, therefore eliminating objections which 
would have been fatal to other forms of construction. Besides this 
the important item of economy has been met in a most satisfactory 
way. I cannot give the actual figures of cost, but I will say that, 
aside from any other consideration, they had a vital bearing in the 
selection of concrete. We wanted the best possible form of con- 
struction regardless of the mere item of expense, and we have not 
only obtained it, but at the same time have saved money. 

31 



Novelty in Concrete Sewer at IMoline, III. 



BY J. W. PAGE. 
(Of Pa«:e & Shnable. Contracting Engineers and Builders.) 

One of the pioneer concrete sewers, which will be in its present 
good condition when similar works of other materials have disin- 
tegrated, was constructed by our firm at ]\Ioline, 111., in the face of 
great difficulties, and has withstood a test which has convinced 
everybody interested as to its permanent qualities. It is a 7-foot 




coxcRiyiK si:\vi:r at molini-:, ill. 

(From photo^rai)li taken aftLT tlu- filliiik'-iii on one side was partially conii)letL'd.) 

pipe, built of crushed stone, sand and cement. The proposition, 
when we undertook the job a little over a year ago, was not an 
alluring one. The route was on the property of the Davenport, 
Rock Island & Northwestern Railway at Moline, and its course was 
for 1,500 feet through an abandoned tail race, where the sewage 
from a drain at the east flowed sluggishly to an outlet draining the 
tail race at the south. The ditch was filled for about 20 feet or 
more with slimy mud and water and we were compelled by our 
contract to keep this sewage flowing without interruption while the 
w^ork of constructing the concrete sewer was in progress. When 
we started the work it was decided to go to the bedrock by excava- 
tion. A ditch was dug at one side and the sewage turned into this 

32 



for passage. By pumping out the water and shoveling out the mud 
and sHme we were enabled to get sheathing to the bedrock, and 
the first concrete was laid to a depth of two feet from wall to wall 
of the sheathing, a distance of 12 feet. When this had set the 
walls were built with forms between them and the sheathing, and 
as they reached completion braces were put up every four feet and 
the backs wedged so as to remove the sheathing braces to make 
room for the arch. This arch w^as built over forms with 2x4 lag- 
ging, of a very rich mixture of one part of cement, two of sand and 
four of stone. Arch and sidewalls tapered from 18 to 12 inches in 




CONCRETE DRIVEWAY AND BRIDGE (WITH GRANITE FACING), 
IN JACKSON PARK, CHICAGO. 



thickness'. Forty-eight hours after laying the concrete the forms 
were taken out. From 40 to 50 feet were constructed daily in this 
manner, the concrete being thoroughly tamped into the forms from 
the top. At the completion of this sewer it received a test which 
gives a very fair idea of the great strength of concrete work. The 
raihvay company had caused this work to be done with a view to 
filling up the old tail race and using it for yardage purposes. It 
was the original plan to fill in on both sides of the new sewer at 
once, but in December it was decided to hurry the filling, and this 
could best be done by making a solid bank at one side of the pipe 
first. The result was that one side of the ditch was filled, throw- 
ing the combined weight of the filling material and the mud against 
the concrete pipe and leaving the other side unprotected. But there 
was no deflection and the concrete withstood the immense strain 
of thousands of tons without a crack or break of any kind. 

Another interesting concrete structure is the bridge at Sixty- 
third street in Jackson Park. This is 180 feet long and is 78 feet 
wide over all. It supports a boulevard upon its surface and a gran- 
ite facing on its walls. It w^as completed last September and bids 
fair to last until the proverbial Doomsday, as it is one of the best 
jobs of the kind that ever came under our notice. In letting the 
contract for this bridge the South Park Commissioners specified 
that it should not deflect more than a minimum of ^-inch when 
the forms were removed and a twenty-ton roller placed upon it. 
When the final tests were made it was found that the deflection 

33 



could not be measured with the appUances in general use. This 
bridge has a 14-foot rise. Capping the piling the abutments were 
built the entire length. These abutments are of concrete, 20 feet 
thick at the foundation and 13 feet 6 inches at the water level, the 
concrete extending through the arch in a thick mass of from 6 feet 
at the veering to 2 feet in the center. Twenty-two tons of steel 
were used in the construction. The steel beams were laid at inter- 
vals of 4 feet and the sections of concrete were laid from abutment 
to abutment. In order to build the bridge a coffer dam no bv 140 
feet was built and the water pumped out, leaving 99 feet in the 
clear. In this space some 400 piles were driven and on them were 
placed the forms for the arch and end work. The arch was next 
constructed and planks put over tlie l(>j) as lagging;-. \Micn this 




CONCRETE SUBWAY COXXEC'I INd 1 HK ROCK ISLAM) RAILWAY BUILDINGS 

AT MOLIXE, ILL. 

was done the concrete was spread and heavily tamped. The perfect 
character of the work is shown by the fact that when the forms 
were removed there w^as absolutely no deflection. The concrete is 
self-supporting and the mass of 6 feet in thickness at the haunches 
is ample for sustaining the 2 feet in the center of the arch. The 
bridge is faced with granite, this being put on as a separate side 
wall, except that headers and stretchers were used to cause the 

34 



stone and concrete to knit, and as a consequence the concrete bears 
a portion of the weio;ht of the granite side walls. 




CONCRETE ABUTMENT FOR BRIDGE IN 
JACKSON PARK, CHICAGO. 

From tests we have had made at this bridge for our own satis- 
faction we are of the earnest opinion that it is much better and 
cheaper than one built of steel or stone, and will last much longer. 



Concrete Construction in Chscago's Public Worlds. 



BY W. A. SHAW, 
(Concrete Expert of the Board of I^ocal Improvements.) 

The use of concrete in public works of a permanent character in 
Chicago — that is in sewers, pumping stations and other building 
foundations and conduits — has thus far been somewhat meager and 
limited. But the idea is gaining ground, as the result of practical 
demonstrations by private builders, and in addition to the street and 
bridge work the city is now using concrete in large quantities, 
especially in the Thirty-ninth street pumping station, where 8,000 
yards were put in last year before freezing weather stopped the 
work, and twice as much more will be used this season. 

Exhaustive tests of concrete mixtures have been made by offi- 
cials of the city engineering department, some of which, notably 
those of P. C. McArdle, demonstrate that concrete made with ce- 
ment, screenings and crushed limestone sets as quickly and exhibits 
greater tenacity of particles than that made with sand. Engineers 
are not wholly agreed as to these results, and it is a question in the 
minds of many as to which mixture wall stand the longest. Con- 
crete mixtures are not as yet a settled proposition and cannot be 

35 



specifically prescribed by any one formula. It is necessary to take 
into consideration the nature of the work of which the concrete 
is to form a part. The general purpose is to secure as compact and 
solid a body as possible, though usage has a great deal to do with 
the degree of compactness required. To the layman, doubtless, the 
simplicity of the construction of concrete is remarkable, though engi- 
neers have been experimenting with various mixtures for years. It 
is known that extreme heat will cause granite to fall apart, and 
limestone to burn into lime. This clement must enter into all con- 
crete making, though limestone appears to be the most available and 
satisfactory. 

Percentages have been established regarding voids in materials 
for concrete making that show such spaces to exist in the various 
available materials as follows : Crushed limes-tone, 40 to 50 per cent, 
of voids ; sand, t,t, to 40 per cent. Thus, theoretically, the sand fills 
the voids in the stone, and the cement must be introduced in suffi- 
cient quantity to fill the voids in the sand so as to obtain a mixture 
of absolute solidity which will knit itself into a homogeneous mass. 
The solidity required governs the richness of the mixture. The sur- 
faces of the materials bound by the cement are the best, logically 
speaking, which are strong and rough, and which will permit the 
setting cement to get the firmest hold. If the mixers and layers 
exercise the proper care and caution the results will be a concrete 
such as is called for by the specifications. But the workmen are 
sometimes careless, and it has been customary to make a richer mix- 
ture than really required in order to counteract this possible care- 
lessness, on the principle that it is cheaper in the end to spend a 
few dollars in "making sure" than to chance failure. However, in 
writing specifications this fact is not considered and contractors are 
expected to deliver the article called for. 

The scientific idea is to make six yards of concrete from one yard 
of cement, three yards of screenings or sand, and six yards of 
crushed stone. Here are nine yards of material conjoining in such 
a manner as to make a mass of only six cubic yards. How is this 
possible? Because the one yard of cement fills the voids in the two 
yards of screenings or sand, and this voidless three yards of mix- 
ture in turn fills the voids in the six yards of stone. While theoret- 
ically this is correct, it is found in practice that while the 45 per 
cent, of voids in the stone are filled, and the 40 per cent, of voids 
in the screenings or sand are also filled, there is some increase in 
volume on account of variation in voids. But upon this proposition 
is based the effort to secure the most compact article possible, and 
such materials as will produce the most compact mass are nat- 
urally sought. 

It is because of its adaptability in mixing to a mass free from 
voids, and also its form which aids in binding, which has led the 
men who make the tests to declare in favor of screenings. But as 
to the durability and qualities other than firmness and compactness, 
it remains for time and the tests of nature to demonstrate which is 
best. 



The largest job of concrete work which the city of Chicago has 
thus far undertaken is the new pumping station at the foot of 
Thirty-ninth street and the lake. This station, which will be utilized 
in driving the sewage flow from the southern section of the city to 
the river and drainage canal, is being constructed largely of con- 
crete. In connection with it has been constructed the largest coffer 
dam ever built on the lake. It is 300 feet in width. The founda- 
tions for the concrete are begun 30 feet below city datum, and 
various walls 9 feet in thickness at the bottom and 6 feet at the 
top reach from the shore to the eastern end of the structure. This 
wall will enclose the pumping machinery which will be placed on 
founded bases made a part of the concrete floor which is 3 feet 
thick. The formula for the concrete used in this work is one part 
of cement, three of sand and six of crushed limestone. 



Features of Concrete Sea-Wall at Lincoln Park. 



In the remaking of the lake beach at Lincoln Park there is a 
most convincing example of the value of crushed stone concrete. 
Several years ago concrete walks were laid upon the site of those 
recently completed, and back of them, was a retaining wall of the 
same character. This work, however, had been built without due 
consideration for the action of the water, and before the park com- 
missioners were aware of it the waves had undermined the sea-wall 
and caused it to fall, and with it the walks as well. These struc- 
tures were made of gravel, sand and cement. When it was found 
necessary to reconstruct this work with a view to withstanding the 
action of the waves, there was an extended discussion. At first it 
was virtually decided to build that part of the wall which would be 
under water out of granite blocks, the plan being to extend the 
granite above the water line and then top it off with crushed stone 
concrete. Supt. Reuben H. Warder had found by experience that 
crushed stone concrete develops into a homogeneous mass and after 
setting is as solid as natural stone, having the additional advantage 
of being able to resist the disintegrating elements to which natural 
stone is subject. Knowing the real value of concrete, he recom- 
mended that it be used for the work under the water line as well as 
elsewhere. All that is essential in order to secure the best results is 
to have the concrete set properly and without any water action dur- 
ing construction. Under these conditions it makes a beach floor 
that is superior to granite block, and, as it is not made up of 
separate pieces as in the case of a floor built of natural stone, it is 
sure to give longer wear. 

In this work at Lincoln Park mixtures were used which varied 
all the way from one part of cement to six of stone, down to equal 
parts of the same materials. The filling for the concrete was gen- 
erally of two parts, sometimes of screenings and sometimes of 
torpedo sand. For finishing the torpedo sand w^as most employed, 



but for the work which required the most perfect set in the shortest 
time screenings had the preference, as it had been demonstrated that 
they are far superior to sand for this purpose. 

Supt. Warder says the first work to be done in the rebuilding of 
the beach was to sink the anchor and lake piles at the outer edge of 
the work. Piles were driven at intervals of i8 inches the entire 
length of the water front to be protected. Sixteen feet back of these 
another row was similarly set. This made it possible to introduce 
the Wakefield sheeting of oak timbers 8 inches thick and 12 inches 
wide. The intervening space was filled with broken boulders, clay 
and stone. Over all, on the sides and top was placed a facing of 
concrete. The top of the rip-rap compartment was treated with a 
covering of concrete, composed of one ]:)art of cement, two of 




((FIRST CONCRETE BRIDGE ERECTED IX THE UNITED STATES.) 
lit was built in Eden Park. Cincinnati, O.. by Reuben S. Warder, in 1894.) 



screenings and five of crushed stone. This makes part of the 
shallow beach which drops off into six feet of water at the outer 
edge. Commencing from the inside line of the crib the concrete 
work begins at 2 feet below city datum. Its inclination is gently 
upward for 60 feet. (The old wall, which was washed away, was 
built at the same point in 40 feet.) 

The principle Supt, W^arder has endeavored to carry out in this 
work is to leave no chance for water to get under the structure. 
Also to construct the beach at such an angle that the waves could 
not dash against it, but would slip quietly over its surface whenever 
there was a contact. This was secured by starting the concrete 
work 2 feet below the city datum where the rush of water is com- 
paratively small. This was where the preceding wall had been de- 



ffectively designed. With the present structure the waves break 
and come up in rollers over the smooth surface, there being no part 
which offers resistance. The slope of the beach is built of heavy 
<:rushed limestone. On top of this sloping wall is a sidewalk from 
i6 to 20 feet in width. This walk is constructed in sections of 20 
feet lineally, with building paper between each section to permit 
■of a slight give and thus obviate any possibility of cracking. Then 
•comes the concrete steps and retaining wall, and back of these the 
parapet. The thickness of the concrete landward varies from 9 
inches to 2 feet, the thinnest point being at the rip-rap. It is for the 
most part constructed of crushed limestone running from j^ to i 
inch in size. 

"I am not inclined to be fastidious about materials," says Supt. 
Warder. "While the rapidity with which a fine article of concrete 
may be obtained with cement, screenings and stone has its advan- 
tages, I would not like to say that screenings are better than sand ; 
•and, on the other hand, conditions do not warrant a statement to 
the contrary. I believe that with all things equal I would use 
■screenings. They are clean and white, and any foreign matter can 
t)e easily detected. Besides, they aid in the setting and filling of the 
cement. Some people might take the most perfect ingredients and 
make a concrete I could not accept. The voids must be filled, other- 
wise the concrete is not what it should be. It can be readily seen 
that screenings work into the mixture easier than sand, and this tends 
to do away with voids. 

''My first work with concrete in a large way was when in charge 
of Eden Park, Cincinnati, where I built a structure 120 feet long, 40 
feet wide, 60 feet above the groimd and carrying a driveway on top. 
This bridge is constructed entirely of concrete and is one of the 
first structures of the kind erected in this country. I had watched 
•closely what was being done in Germany and other European lands, 
and was so absolutely certain of the results to be obtained that I did 
not hesitate to build this concrete bridge. It is reinforced with iron 
rods, but looks to be just what it is — concrete. There is no stone 
facing or imitation of stone work on it. I prefer to have things ap- 
pear just as they are, and that is the way with this bridge. It has 
"been in place now since 1894 and there is not a crack or a split in its 
surface. It is as solid as if hewn out of rock, and at that point is 
-even more solid than if made out of the natural rock upon which it 
-stands. The reinforcement is moderate so as to avoid excess of 
vveight. The curve of the arch in the concrete is sufficient to hold 
the structure. The concrete is made of crushed limestone, and this 
is the best, in my judgment, as the rough edges have a binding 
<[uality which, if the concrete is properly mixed, will set in a mass 
absolutely unaffected by jar or motion, as the interior of the com- 
position is angular and practically dovetailed at every conceivable 
point. 

"The day of the concrete age is only dawning. The strides in 
the use of the composition have of late been wonderful, but we are 
•only at the dawn. Great minds and brains are working untiringly 



to perfect its uses and results are slowly appearino-. The attitude 
of builders should be to use the most approved methods at the date 
of the work to be done. If this policy is adhered to we must all 
admit that for outdoor work crushed stone concrete is without an 
equal." 



Concrete Formula for Chicago City Work, 



BY J. H. SPEXGLER, 
(Engineer for the City of Chicago.) 

To secure satisfactory material for the river piers, tail pits and 
anchor piers of its numerous bridges the city of Chicago has adopted 
a concrete formula which crucial tests have shown to meet every re- 
quirement from the water-resisting standpoint, as well as- those of 
sustaining qualities. This formula, or mixture, consists of one part 
of cement, three parts of sand or crushed stone screenings and five 
parts of crushed limestone. Occasionally this is varied by the sub- 
stitution of sand for the screenings, but whenever it is possible to do 
so we eliminate the sand entirely. Tests made by the citv engineering 
de])artment show that for a combination of waterproof and weight- 
sustaining qualities this mixture is far superior to that obtained by 
any other combination. Water tests demonstrate the fact that prac- 
tically no impression is made on the homogeneous material when 
faced with four inches of a mixture of one part of cement and two 
of torpedo sand. Water has no effect whatever upon the setting 
which continues under immersion, as in the air, for about a quarter 
of a century before the limit is reached. The facility with which 
these concrete foundations and abutments for bridges may be placed 
is only one of the important features of the material for this special 
use. It is far cheaper than stone work and the best of masonry does 
not attain the solidity of concrete. 

All the new bascule bridges built by the city of Chicago are 
constructed on the same general plan, with only a few changes in the 
form of the tail pits. About 5,000 yards of concrete is placed in the 
sub-structure of the ordinary bridge. The construction of the West 
Division street bridge last year affords a good illustration of the 
average style of the work. Two years only wTre occupied in the 
job, dating from the day the first pile was driven to the opening of 
the structure for traffic, and considerable time was lost in waiting 
for steel at that. All the concrete work is faced to a point 16 feet 
below the surface of the river and was allowed about a week to set 
before the water was allowed to run upon it. At the outside of the 
piers of finished structure protection piling is erected to prevent pos- 
sible injury through collision w^ith boats. 

As to results, particularly as concerns the concrete work. I am 
positive the piers and abutments will never give out. provided they 
are maintained under the care of competent and intelligent inspec- 

40 



tors. Neither is there any chance for disintegration when the con- 
crete mixture is made according to the formula prescribed in our 
specifications. Given clean materials — good cement, screenings and 
crushed stone — in which no foreign substances are incorporated, a 




COXCRETK PIERS AND TAIL-PITS FOR BRIDGE AT WEST DIVISION ST., 

CHICAGO. 

concrete will result which will stand every possible test of strength 
and endurance, and at the same time will be nuich more economical 
than dimension stone or any other material which can be employed 
for similar purposes. 



Merits of Screenings in Street Paving. 

Concrete in street paving — viewed from the standpoint of dura- 
bility — is looked upon as being fully as essential as the right of 
way. Permanent foundations are thus secured. The specifications 
furnished by the city, and under which all paving work is done^ 
provide for the use of crushed limestone in making the concrete. 
Under a special order of the Board of Local Improvements issued 
last season the substitution of limestone screenings for sand was sug- 
gested and the results were so satisfactory that instead of an 
emergency order being revoked it is still in force. A large amount 
of screenings are now being used in street paving in Chicago with 
entirely satisfactory results as to the quality of the pavements and 
something of a saving in cost. The importance of crushed stone 




COXCRKTK STAIRWAY AT M AR.Si:iLLi:S. ILL 



in street paving may be best considered when it is known that for 
the better grades of street improvements of this nature the cost 
of the stone is from 25 to 30 per cent, of the total cost of the work, 
and this latter 'ncludes the expensive item of labor. In street pav- 
ing this item of cost is just now one of absorbing interest to the 
property owner, and it is the feature which is causing the most dis- 
cussion. The people of Chicago want what is the best and at the 
same time the cheapest, and the best is in the end almost invariably 
the most economical. If a paving foundation does not warp, spring 
or crack from the frost its durability is unlimited, and this is what 
has been found in concrete. The city insists upon a concrete founda- 
tion made of crushed stone, this decision being reached after long 
experience. The specifications provide for this material to a depth 
of 9 inches. Gravel is not permitted to be used in the foundations, 
and the only logical deduction is that the crushed stone is superior. 

42 



But the value of crushed stone concrete is now almost universally 
admitted, and the main question is that of cost to the property 
owner. For a few years past there has been a fluctuation, and 
latterly an increase in the price of crushed stone. The problem to be 
solved is this : Is the cost of paving higher to-day, proportionately, 
in comparison with other finished works in which labor is an im- 
portant factor, than it was three years ago? Here are a few figures 
covering the cost of paving in 1903, which may be of interest in this 
connection : 

Highest price per square yard for contracts let last year, calling 
for 9 inches of limestone and 3^ inches of granite per square yard, 
$1.35. This is the highest for ten years. 

Lowest price per square yard for 9 inches of crushed limestone 
and 41^ inches of granite, $1.10. 

Eight jobs, calling for 9 inches of crushed limestone and 3^ 
inches granite; average price per square yard, ^1.22^. 




CONCRETE STAIRWAY, CARRIAGE STEP AND CURBING. 
AT MARSEILLES, ILL. 

Highest price per square yard for 8 inches of slag, 3 inches of 
limestone and 3^ inches of granite, $1.52. Lowest price for the 
same materials, $1.20. 

Twenty-four jobs, calling for 8 inches of slag, 3 inches of lime- 
stone and 3^ inches granite ; average per square yard, $1.36. 

These figures will show what crushed limestone concrete is cost- 
ing in street paving as compared with other forms of foundation 
construction, The average is 13^ cents per square yard less. The 
highest cost of limestone is 17 cents less than the highest price for 
the slag combination, and the lowest price for the limestone is 10 
cents under the lowest for slag. The price of stone has advanced 
very slightly since 1900, considering the marked increase in the 
values of other materials, and this is all the more significant when 
the excellent service for the delivery of stone is taken into ac- 
count. 

43 



"As to screenings in street paving," says a prominent con- 
tractor, "there is a decided advantage because the deUveries are 
much better than those of sand, while the results so far as the con- 
crete itself is concerned are fully as good, and perhaps a little bet- 
ter. But the most important item of all is that the screenings are 
cheaper. It takes the screenings a trifle longer to dry out in the 
concrete than it does the sand, but the mass formed from the ma- 
terial which takes the longest to dry naturally becomes the stronger. 
It is just about as easy to work wet screenings as sand. As a result 
of the order of the Board of Local Improvements permitting a sub- 
stitute for sand my firm laid 200,000 square yards of paving foun- 
dation last year and used in the work 3.4076 yards of crushed lime- 
stone and 13,093 yards of screenings. The deliveries of these ma- 
terials were made in such good shape that the work was done ex- 
peditiously, and the stretches of pavement are in the finest of con- 
dition and will last indefinitely. The use of screenings would not 
have been permitted if they were not known to be equal in quality 
to sand; and many experts believe they are superior, as they make a 
more solid bond and tend to create a more homogeneous mass." 



Crushed Stone the Best Road Material. 

BY JOHN M. HAZEN. 

(The Improvement Rulletin, Miuneapolis. Minn.. Ai)ril '.». 1904.) 

The proper ballast to nn'x with cement mortar for concrete ; the 
cheapest and best material for ballast for railroads and the only 
material to put our highways in first-class condition, is crushed 
stone. The most economically maintained railroad track or highway 
is the one that is always in first-class condition. While the first 
cost of crushed stone may seem expensive, the best that can be had 
is none too good for the proper maintenance of a road-bed. With 
crushed stone for ballast the life of the tie is prolonged, the road-bed 
well drained, free from dust, etc. Other things being equal, the 
maintenance thereafter is reduced to the minimum. 

It is only within the last few years that railroad companies have 
adopted concrete to any great extent, but it is coming more and 
more into use, and nov; most of the Eastern and some of the Western 
roads are using it largely in the construction of bridge piers, cul- 
verts, retaining walls, freight houses, turntable pits, floors, walks, 
piles and ties. The conclusions to be drawn are that crushed stone 
and cement are the best material that can be had for such pur- 
poses. 

For footing for foundation walls and foundations for bridge 
piers below water level there is nothing equal to it. Wliere cribbing 
is used a good foundation can be laid in the water, but care should 
be taken in depositing the concrete, to be successful ; some lower 
it in paper sacks, some in thin cloth sacks, but the best and most 
satisfactory way is to lower the concrete in a bucket or dipper with 

44 



a hinged bottom that can be opened with a Hne when the dipper 
reaches the desired depth. Otherwise if the concrete is dumped 
into the water the cement will wash out and only the stone will 
find the bottom. It is the cheapest and best for footings for build- 
ings, for it enables the builder to form his base as wide and deep 
as he likes', with no ragged edges, level on top, ready for the wall. 
One can hardly realize the various uses that crushed stone is put to 
at the present time, and engineers are looking for and finding some 
new manner of using it that is economical and at the same time 
gives the required strength. 

The size that stone should be crushed and screened to depends 
upon the use to which it is put. For road metal for macadam, three 
inches would be none too large for the coarsest, and from that down 
to one inch, or perhaps less. For concrete two inches is about the 
size the largest cubes should be, and from that down to one-quarter 
of an inch. For flooring one inch down to one-quarter inch 
is the proper size. For roofing, one-half inch down to one-eighth is 
just right. It is far better than gravel, for, being curbed, it will not 
wash out. 

Quality is a very important factor in crushed stone for con- 
crete. Avoid all rusty or dirty stone ; thin stone quarried near the 
surface of the ground. Use nothing but absolutely clean, firm, 
hard stone, and the concrete, when thoroughly set, will have a crush- 
ing strength equal to the stone of which it is' made. 

Do not expect good concrete made with poor cement. It is a 
mistaken idea that almost any brand or kind of cement will make 
concrete good enough and strong enough after it is covered up for 
ordinary purposes. That is wrong, as many users of that material 
will testify. If satisfactory results are wanted good material must 
be used. 

For good concrete the stone must be of various sizes, from two 
inches down (crusher run), so that there will be no voids after the 
concrete is rammed in place. If there are voids the concrete is 
weak. One can figure on just as many cubic feet or yards 
of crushed stone as the space measures that is to be filled, for 
if properly made the stone fills the voids and the cement and screen- 
ings merely cements the cubes together. 

Clean limestone dust has been found to be a good substitute 
for sand for concrete. 

This short article would hardly be complete without at least 
mentioning macadam roads. There is much to be said in favor of 
macadam for our highways, but the limited space will allow of only 
a mere mention. Of all the states, Minnesota is as well, if not bet- 
ter, prepared with material, money, intellect and a general desire 
on the part of the farmers, whose needs exceed all others for good 
roads, as any state east or west, and yet the indifference, and to 
some extent, hostility of our legislators at the last session prevents 
the use of material at hand — and in such great abundance — to the 
detriment of the farmers, whose highway is their railroad. With 
our material and soil to build upon and willingness on the part of 

45 



the people to build, there is no excuse for poor highways in Minne- 
sota, provided they have half a chance. 

We want the authority of our state legislature, which will be 
backed by the United States Government, and if the Brownlow bill 
passes, will be materially aided financially, so that some of this 
valuable road material can be utilized and we who are living to-day- 
get some benefit therefrom. 



Exacting Tests in Concrete Construction. 



BY GEORGE F. JENKINS, 
(Construction Superintendent for Geo. B. Swift 6c Co., Chicago.) 

In the construction of the nine buildings which make up the 
Rock Island Railway division shops at jNIoline, 111., concrete was 
probably given as broad a test as anywhere in this part of the coun- 
try, and the result has been all that could be desired. Some 20,000 
yards of this material were put in the foundations and other work, 
which include the engine bods, engine stall pits, tunnel, water- 
tables and foundations. There is a great deal of concrete work 
which is exposed above ground, and of this every inch is in fine con- 
dition, the lines and angles being as perfect as could be secured by 




CONCRETE ROUND-HOUSE AND TURN-TABLE AT MOLINE. ILL. 



the use of sawed stone — and it is cheaper. The finish for all th:s 
work was made in its construction. We laid the concrete very ;vet, 
and in some cases the amount of water reduced the mixtures to 
almost slop. This was tamped well, and the sloppy cement and sand 
came to the surface, where it was leveled and trimmed, leaving a 
perfect facing and one which will stand any test of the eleii-cnts. 
This feature of the work has given remarkable results. The sur- 
faces are as smooth as a plastered wall, though the usual cement 
mortar finish was not especially put on. 

Another innovation in this work was the making of the water- 
tables of concrete. These were built upon the foundation wall?, and 

46 



the brick work for walls was founded upon them. The stone tables 
were entirely dispensed with, and from the results obtained it is 
apparent that the use of concrete in this feature of building will be- 
come general. 

The soil on the site of the shop buildings is sand, and the con- 
crete work is founded throughout on the sand, but no difficulties were 
met in getting a proper base for the walls. We used in the making 
of the concrete a IMcKelvey mixer, and the following proportions of 
materials : 

Foundation and general work — cement, one part ; sand, three 
parts ; crushed stone, six parts. 




CONCRETE FOUNDATIONS ROCK ISLAND RAILWAY SHOPS AT MOLINE, ILL. 



\\'atertables and turntables — cement, one part ; sand, two parts ; 
crushed stone, four parts. 

In the building of the turn table basin and pier, concrete ties 
were introduced, probably for the first time in the West, at least. 
The ties were not made with block concrete, but are a portion of the 
bench wall structure raised three inches above the bench wall floor 
and constructed with arrangement for an expansion bolt with which 
to secure the rails to the tie> In the center of the turntable the 
swinging-table pier was constructed in the dimensions of 13x13 feet 
and 9 feet high. 

The only piece of reinforced concrete work in the terminal 
building is the floor of the power house. This was laid in spans of 
eight feet and reinforced slightly. There are ten buildings in the 
group. 

One of the largest pieces of concrete work is the timnel which 
connects all the buildings in the group. The tunnel is built with four 



walls, its general dimensions being 6 feet wide by 6/2 feet high, 
though between some buildings- it is somewhat smaller. It is used 
for the carrying of water pipes, wires and steam connections. In 
construction, the floor was first laid, then the two side walls weie 
built in forms and the top covered over with a verv slightlv rein- 
forced concrete slab, making the interior of the tunnel almost sr;uare 
in form. 

In the making of the concrete two-inch crushed limestone was^ 
used, it being a tried and reliable basis for the purpose, and in this 
work it was necessary to have the construction so nearlv perfect in 
every way as possible. 

Another interesting work in concrete construction done bv this 
company is the building of foundations for the Illinois Central Rail- 




ENGINE FOUNDATIONS OF CONCREIR IN RAILWAY SHOPS 
AT MOLIXE ILL 



way grain elevators at Xew Orleans. This work contains the first 
successful basement ever used in that city. It is constructed of con- 
crete and has since been extensively copied there. The immense 
elevator rests upon a piling, rising from which is the concrete foun- 
dation for the elevator and power house. The ground measure- 
ments of the elevator structure are 100x320 feet, and those of the 
power house 69x111 feet. The elevator is close to the levee, where 
the ground is somewhat soft. The piling was driven and the con- 
crete foundations placed upon it, and upon that the timber con- 
struction was erected. The foundations were calculated in resisting 

48 



powers to sustain the capacity of the elevator, which is 1,200,000 
bushels, besides the weight of the building and the foundations them- 
selves. The foundations for this building are of the highest class 
and have revolutionized the concrete construction at New Orleans 
and the method of concrete mixing in all parts of the country. 

The concrete was almost entirely mixed of one part of cement, 
2^ parts of sand and six parts of crushed limestone. 



Concrete for Track Elevation Purposes, 



BY G. W. VAUGHN, 
(Inspector of Track Elevation for the City of Chicago.) 

My special duties for the past four years have been to act as a 
representative of the city of Chicago in the inspection of railway 
track elevation. Under the instructions of Supt. O'Neill, chief of 
this department, I have given my time almost wholly to the work 
being done along the route of the Santa Fe line, and so far as this 
particular road is concerned I can well say that the facilities afforded 
for arriving at exact conclusions have been unusually satisfactory. 
This is especially true as to the merits of crushed stone concrete, 
the use of which forms one of the most important features of suc- 
cessful track elevation. The substance of my observation in this 
connection is that concrete made in this way (with crushed stone) 
is the only material that will fully meet the requirements. About 
36,000 cubic yards of this kind of concrete have been placed in re- 
taining walls under my supervision and of all the work of this 
nature which I have seen I can point out none other so perfect in 
every essential respect. 

All the retaining walls along the Santa Fe roadway in Chicago 
are constructed solely of crushed stone concrete. The work, which 
is very extensive in scope and naturally involves the expenditure 
of an immense amount of money, was undertaken against the judg- 
ment of railway experts and officials directly interested. When the 
track elevation ordinances were enacted there was a loud protest, 
but to-day every intelligent operating official recognizes the wisdom 
of the new policy, not only as securing more safety and speed in 
the handling of railway business, but also as a matter of actual 
economy. The danger of loss of life at grade crossings is being 
gradually eliminated, trains are being moved with much greater 
rapidity, wrecks are less frequent, and the railway men themselves 
have come to be the warmest advocates of the elevated track sys:- 
tem. With this change of heart has come a desire to make the 
work of the most substantial and enduring character, keeping in 
view real economy as to future results. It is with this purpose that 
crushed stone concrete now enters largely into the construction of 
the retaining walls, abutments, viaduct piers, culverts, etc. The 
railway officials, convinced that track elevation is a good thing, 
want it done in the best possible manner. 

49 



It is only fair in an article of this kind to say that the present 
very agreeable conditions are largely due to the intelligent efforts 
of Supt. O'Neill. The first really big job was done at the Sixteenth 
street crossing, where all sorts of annoying delays were feared and 
serious engineering problems encountered. Despite these drawbacks 
128 trains were kept moving every day with but little interruption 
while the work was being done. It was at this crossing that the 
question of the proper material for the abutments and foundations 
first arose. Realizing that the work must be of a substantial and 
permanent nature, Supt. O'Neill and the railway officials gave the 
subject deep consideration. They started out with the firm belief 
that dimension stone would be the most satisfactory, and this was 
also the opinion of the track elevation committee which had charge 
of the work at that time. Careful study, however, developed the 
fact that crushed stone concrete would be better in every way — 
cheaper and more lasting, and, after a series of exhaustive tests 
which thoroughly established its merits, this material was selected. 




COXCRKTK FOUNDATION' FOR ILLINOIS CENTRAL RAILWAYS MAMMOTH 
GRAIN ELKVATOR AT NEW ORLEANS. LA. 



About 20,000 yards of this concrete was placed at the Sixteenth 
street elevation. 

To a certain extent, I am glad to be able to say, I am responsible 
for the concrete retaining walls put up along the Santa Fe line, and 
very naturally I wanted to have them as substantial and durable 
as possible, keeping in mind the enormous strain and pressure they 
would have to sustain and at the same time having in view the im- 
portant item of expense. During the time I have been in charge 
of this work the retaining walls have all been constructed of the 
following mix : 

Cement, one part ; screenings or sand, three parts ; crushed stone, 
five parts. 

From this mixture we have obtained results in compressive 
strength and tensile tests which prove beyond doubt that there is 
nothing in the line of natural rock which is superior. I would call 
-especial attention to the finish on these retaining walls. This is a 
subject to which the railways gave a great deal of thought and on 

50 



-which they expended a large amount of time and money before a 
•satisfactory material was delivered to the proper officials for in- 
spection. This finish, which for the last two years has been used 
in all elevated railway work of this nature, is one-half inch in thick- 
ness and consists of equal parts of stone screenings and cement. 
Nothing like it can be obtained by any other process or ingredients. 

At Archer avenue we have several blocks of concrete retaining 
Avails from 5 to 14 feet in width and 20 feet high, which retain 
something like 40 tons of filling to the yard of wall surface. These 
walls are built in steps and the weight is not all to the outward, the 
pressure being diverted from the top downward as well. This 
pressure from the top ameliorates that towards the sides and the 
walls therefore stand up well under extraordinary conditions. 

If it were not for the manifest advantages of concrete, railway 
track elevation in Chicago would be a much more serious and ex- 
pensive problem than it now is. It has been amply demonstrated 
that concrete walls can be more cheaply erected, more quickly put 
in place and afford more solid and lasting results than those of 
stone. 

Railway Round-House Built Entirely of Concrete. 

BY WILLIAM GRACE. 
(Head of the William Grace Construction Company.) 

While we have never as yet constructed a building entirely of 
concrete in Chicago, we are now completing for the Canadian Pacific 
Railway, at Moose Jaw, Assiniboia, a round-house which is made 
solely of this material. It is of the reinforced pattern, but it is 
concrete from foundation to pinnacle, including the roof, walls, 
stacks, pits, turn-table basin and all. This structure, which is now 
almost completed, is not exactly an experiment for the Canadian 
Pacific, as other concrete works along its lines have been eminently 
successful. It is, however, something of a satisfaction to knov' 
that the company has let the contracts for this work in the city of 
'Chicago. The round-house contains fifteen engine stalls. The gen- 
eral dimensions are : 300 feet around and 120 feet from outside wall 
to outside wall. The walls are 3 feet 4 inches at the base and taper 
-to 18 inches at the gutter, 20 feet above the foundations. The win- 
dows were built in forms, and the walls were guided by braced 
lagging. No reinforcing was used in the walls, and the steel for the 
frame work of the roof was set in the walls but slightly. The struc- 
ture will be a model in its construction, and will probably be used 
.as a precedent for permanent railway improvements in the North- 
west. The work is as cheap as the temporary work done by most 
-roads on new portions of the lines, and will last indefinitely. 

In at least two large structures which we have erected in Chi- 
cago concrete has played an important part in the foundation and 
other heavy features. These are the La Salle street station, other- 
-wise known as the Rock Island depot, and the Hibbard, Spencer & 



Bartlett warehouse building at State and South \\^ater street.^ and 
Wabash avenue. At the La Salle street station all the founJlation 
and piers are of concrete. Some of the larger piers for the vaults 
rest on a floating base, but the greater part of the wall foundations 
are sunk to hard-pan. All around the outer dimensions of the 
train sheds concrete foundations were put in, and all the piers upon 
which rest the columns which support the score of tracks rLiiining 
into the sheds are of concrete sunk to a depth of about 14 feet. Be- 
sides this the entire floor space of the great train shed is surfaced 
with concrete over the steel work. The first difiiculty we met in 
this undertaking was when the excavation was completed and we 
were ready to begin laying the concrete. We had placed a crushing 
machine and mixer on the ground, and to obtain the crushed lime- 
stone which was to be the principal feature of the concrete we pro- 
ceeded to work over all the good stone of that kind left in the old 
building. In the crushing process a large amount of screening.-? were 
obtained, and these we proposed to utilize in the concrete as a sub- 
stitute for sand. To this the engineers representing the interests of 
the railway objected, contending that the product would not be as 
durable as that made with s^nd. We insisted that it would be better 
in every way, and to settle the matter we submitted to Captain 
Robert W. Hunt several samples of sand and screenings concrete 
to be tested as to compressive and tensile strength. We also had 
that gentleman make laboratory tests of mixtures of cement and 
sand, of screenings and cement, and of a mixture of sand and 
screenings and cement. The results of these tests were such that 
the railway engineers withdrew all objections to the use of screen- 
ings, and from then on all of this material we could produce was 
utilized in the mixing of the concrete. Capt. Hunt's tests demon- 
strated that the concrete made of screenings and crushed stone, so 
far from being inferior to that produced with sand, was under many 
conditions even better. 

The Hibbard, Spencer & Bartlett building I consider a perfect 
specimen of fireproof warehouse construction. The foundations, 
driveways and partitions are all of concrete made from screenings 
secured by crushing on the ground the limestone in the old struc- 
tures. That is to say, we used this as far as it would go, but there 
was not enough of it, and we later had to obtain our supply of 
screenings from other sources. With due consideration for our 
past experiences and keen appreciation of the uses to which the 
building would be put. we gave crushed limestone preference in the 
mixing of our concrete. The practical builder generally under- 
stands the best and cheapest methods of construction, and I make 
use of the word ''cheapest" solely from the viewpoint of actual 
economy — the obtaining of results that will meet the most exacting 
of requirements at the lowest possible outlay consistent with hon- 
est workmanship. All our concrete mixtures have been made upon 
a practical knowledge of the percentage of voids in limestone of a 
given size, and we have regulated the proportions of the other ma- 
terials employed — the cement, etc., — to meet this demand. 



Gigantic Worii on a Concrete Bridge. 



BY RALPH MODJESKI. 
(Of Noble & Modjeski, Contracting Engineers. Chicago.) 

One of the most important jobs of modern concrete construction 
is that of the approaches for the new railway bridge over the Mis- 
sissippi river at Thebes, 111., which is for the joint use of the Illinois 
Central, Chicago & Eastern Illinois, Missouri Pacific and St. Lous 
& Southwestern roads. The entire construction is 4 and 7-10 miles 
in length, of which the concrete approaches take up exactly four 
miles. The east approach, including the concrete arches and 
earth, extends for 2 and i-io miles, and necessitated the excavation 
of 260,000 cubic yards of ground. That on the West end extends for 
I and 9-10 miles. The bridge part proper, which is of concrete 
and steel, is 3,708 feet in length, consisting of five spans, in the 
superstructure of whichh there are 14,000 tons of steel. This 
rests upon six main piers of concrete built upon rocks. Five of 
these piers were constructed by the pneumatic process, and one 
by open excavation, as the solid rock at this point is very close 
to the surface of the river bed. From the bottom of the found- 
dations to the top of the structure it is 231 feet. The piers, in- 
cluding the foundations, are of crushed limestone and Portland 
cement concrete, faced with Roman-Oolithic stone, while granite 
is used for the nose stones and cut-water, and bridge seats. At 
the top of the road-bed, above the bridge floor, and upon the 
concrete walls a coping of stone has been placed, but in the solid 
part of the structure a very little stone has been used. 

In a work of this nature the proportions of the concrete mixture 
are, of course, an important item. These have varied according to 
the resistance required. For the foundations of the arches in the 
approaches, for instance, which begin about 30 feet below datum, 
we used i part of cement, 2 of sand, and 5 of crushed limestone 
for the first foot of concrete laid above the rock. From then up to 
the surface we used i part of cement, 3 of sand, and 7 of stone. 
For the upper parts of the piers, above ground and all pilasters, 
the proportions were i of cement, 23^ of sand, and 6 of stone, while 
for the arches themselves we went back to the original foundation 
formula. Tlie foundation copings and parapets were made of i 
part of cement, 2 of sand and 4 of crushed limestone. The con- 
crete was mixed by machine, deposited in layers from six to twelve 
inches in thickness, and thoroughly rammed with tampers weighing 
fully 20 pounds. In all the arch rings and spandrel walls the con- 
struction was monolithic, and when each was put up the work was 
continuous. To prevent seepage of water through the joints these 
latter were covered with soft asphaltum on the inside of the spandrel 
walls after the centers were struck. 

While the entire structure is on an imposing scale it is the ap- 
proaches that are attracting the most attention in engineering cir- 



lixkvi ^:^."^: 




VARIOUS VIEWS OF THE NEW CONCRETE BRIDGE OVER THE 
MISSISSIPPI RIVER AT THEBES, ILL. 



cles. The foundation? for these are on both shale and rock and 
with the exception of one pier have been open excavation. In the 
approach on the eastern side there are five 65-foot arches of con- 
crete, and on the western end there are six of the same size and 
one of 100 feet. In the construction of these approaches some 35,- 
000 cubic yards of crushed stone concrete has been used. They have 
been subjected to severe tests which have demonstrated to the 
satisfaction of experienced men that, while the steel part of the 
structure may go to pieces in time, the concrete work will last in- 
definitely. 

Concrete Coal Bins of Large Storage Capacity. 



BY W. S. MENDEN^ 
(Chief Engineer for the jNIetropolitan Elevated Ry, Co.) 

Two methods of concrete construction have been employed in the 
erection of the new coal handling and storage house at the junction 
of the Garfield Park branch of the Metropolitan Elevated Railway 
with the Belt Line tracks. In the lower bins heavy, plain concrete 
is used, while the roof and hopper (midway between the roof and 
the funnel) are of reinforced concrete. This structure, which is in 
reality an elevator, has been attracting considerable attention from 
builders and others who have use for similar structures. The build- 
ing itself is 90 feet high, and is made of steel above the level of the 
elevated tracks. The ground measurements are 100 by 42 feet. 
While we do not claim for it any distinction as a model for coal 
handling and storage purposes, yet it is different in many respects 
from any other now in use. The conditions confronting the com- 
pany when it decided to erect the building were such that several 
levels were necessary, and it was imperative to have the storage of 
coal high above the level of the tops of the cars as they stand on 
the elevated tracks. In solving this problem a plan was adopted 
which permits cars to run into the building from the first elevated 
level and also the ground level, while a belt carrier hoists- the coal 
from the ground to the bins 50 feet above. 

The storage room has a capacity of 3,000 tons, and the area is 
in the neighborhood of 3,000 square feet. The floor is built to form 
a trough emptying into the hopper mouth. This floor, which is of 
concrete, and has steel reinforcements 6 feet apart, will sustain a 
weight of 400 pounds to the square foot without causing the slight- 
est impression. No actual tests have been made of the maximum 
sustaining power under weight, but we know what it will do with 
proper reinforcement. In the basement hopper and tunnel the con- 
crete work is of ordinary construction, the excavations being lined. 
About 2,200 yards of concrete were used, which is considerable 
when we stop to think that the building is- only 42 feet wide by lOO 
leet long. All the foundations and sub-work are of concrete, the 
rest of the structure, aside from the equipment, being of steel. The 
mixture of the concrete for the roof and hopper was one part ce- 



ment, two of sand, and four of crushed stone. In thickness the 
concrete work varies, according to location, from 6 inches, which 
is the maximum, down to 3. 

Our company has recently gone into concrete construction quite 
extensively. One of the latest improvements of this nature is a 
switch tower just west of the river which is built entirely of this 
material, reinforced with steel, and it is giving complete satisfac- 
tion. Concrete for walls and foundations is now an article of set- 
tled merit. It is to the investigation of the reinforced variety that 
engineers and fireproofing experts are giving deep thought. 

Engineering Triumph in a Railway Bridge. 

BY E. L. COX, 
(Chicago Agent Ciennan-American Portland Cement Co.) 

The Illinois Central Railroad bridge over the Big JMuddy river 
is one of the engineering feats which is doing much toward the 
furtherance of the crushed-stone concrete idea. This bridge was 
built in a year and five months and is one of the most perfect struc- 
tures of its kind in existence. H. W. Parkhurst, bridges and build- 
ing engineer of the Illinois Central road, was in charge of the con- 
struction, and C. H. Scribner, Jr., was the contractor. Twelve 
thousand cubic yards of concrete were used in the work, which 
covers a distance of 574 feet and 6 inches, lineal measurement, and 
is 34 feet 6 inches wide. It is capable of accommodating two tracks, 
the rails being 50 feet from the base of the arches. The structure 
is built of three non-reinforced concrete arches spanning 140 feet 
each, witli a raise of 30 feet. 

The original steel span bridge rested on three masonrv piers, 
there being only one track. Beginning in January, 1902, the con- 
crete foundations surrounding the piers of the steel bridge were put 
in, and by April the forms for the first arch was being erected. The 
framework of the centers had each of the curved ribs made of two 
pieces of 3 by 12 and one piece of 4 by 12. Braces ranged from 
6x8 to 8x8, and 3-inch planks were used for horizontal ties and 
braces. Piles were driven around the stone piers and the concrete 
piers were built upon them. Sheeting 3 inches thick was used in 
making the skewbacks, which were built before the vuossoirs were 
started. 

In making the concrete a machine mixer was used. In the gen- 
eral foundation the concrete, which was laid within coffer dams or 
sheeting, was proportioned with one part of cement, three parts of 
sand and six parts of crushed limestone. Where heavy masses of 
concrete were required, having a great thickness and carrying noth- 
ing but compressive loads, the centers of these masses were made of 
concrete with one part cement, four parts sand and eight parts 
crushed stone. The bodies of piers, bench walls and walls built 
within molds were proportioned with one part of cement, two and 
.a half parts of sand and six parts of crushed stone. For all arch 

56 



crowns and rings and in general where any tensile strength was to 
be provided for, the proportions were one part of cement, two of 
sand and five of crushed stone. Where special additional strains 
were to be provided for the mixture was one of cement, two of sand 
and four of stone. 

The three arches are not reinforced in any way. The finish is 
of an ornate character, with ornamental copings, a surfacing of ce- 
ment mortar having been applied to all portions of the structure ex- 




CONCRETE RAILWAY BRIDGE NEAR CARBONDALE. ILL. 

posed. Under the heaviest strains imparted by trains, and when 
the forms were removed, there was no deflection in the concrete 
structure. Before the completion of the bridge high water touched 
the arches several feet above the springing line, but no damaging 
effect was resultant. 

This bridge is looked upon as one of the most perfect of this 
variety of construction and is attracting wide and favorable atten- 
tion among railroad men. 



Economy of Concrete Work In Track Elevation. 

Two of the most noticeable and interesting features of the work 
of track elevation now being done bv the P. C. C. & St. L. Rv., the 
C. J. Ry. and the C. T. R. R. at Brighton Park, south of the Illi- 
nois and INIichigan canal, are the mammoth abutments at Thirty- 
ninth street and South Western Avenue & Boulevard and the 
culvert just south of Thirty-ninth street. To engineers and builders 
these works are of special interest as illustrative of the best type 



of heavy concrete construction. Theyllare lasting monuments to 
the tendency of great corporations whicli invest millions of dollars 
in permanent improvements to utilize the most durable of materials 
and at the same -time keep in view the important items of present 
cost and ultimate economy. This work of track elevation is prob- 
ably one of the most complicated of its kind ever carried out. The 
largest subway in Chicago is being constructed at South Western 
Avenue Boulevard and Thirty-ninth street, where there is an open- 
ing of 600 feet from abutment to abutment. 

The largest single block of concrete in Chicago is placed in the 
east abutment wall at South Western Boulevard and Thirty-ninth 
street. It is a mass 370 feet in length, 21.5 feet high from base to 
top of coping, and with an average width of 9 feet 10 inches. The 
mixture is as follows : 

Portland cement, one part ; stone screenings, three parts ; crushed 
stone, six parts. 

To counteract the effects of frost when the concrete had to be 
mixed and laid in freezing weather there was added a small quan- 
tity of salt, about an ordinary shovelful to each batch. The result 
is that all concrete work which was done in a temperature of 20 
above zero has set well and is in first-class condition. As an addi- 
tional precaution tarpaulins and straw coverings were used. 

Between the abutments the bridge will be supported by 95 steel 
columns which will rest upon concrete piers, thus obviating the 
necessity for stone masonry at a very considerable saving in cost. 
These bases, of course, must be of the most durable character be- 
cause of the heavy loads they must sustain, and because they are 
entirely covered up, making it impossible to inspect them and de- 
tect any possible defects. They are 12x12 feet and 14x14 feet on 
the base and 10 feet in depth. The pressure resistance is unlimited 
and will never be completely taxed by any weight that may be placed 
upon them, while their tenure of service cannot be measured in 
years. 

Reverting back to the subject of the abutment walls, which will 
retain several thousand tons of filling on the grade, the following 
cross-section measurements may be of interest as showing the mag- 
nitude of the work : Beginning at the bottom the extreme width 
is 10 feet 3 inches, the next bench is 7 feet 6 inches, and the top 
one 5 feet 3 inches, all of solid concrete. The coping is also made 
of concrete, except the bridge seats, which are of granite. These 
walls are constructed in a series of steps which will help to over- 
come the tendency of the wall to overturn on account of the outward 
pressure by the assistance of the weight of the filling which rests 
upon the benches. The total cost of the work will be about $500,000. 

Crushed stone in varying sizes enters largely into the composi- 
tion of all concrete work on the Pennsylvania road, its advantages 
in many ways having been established beyond question. Its weight- 
resisting qualities, rigidity and weather-defying properties are all 
vital items, and besides these we ha^^e the immense additional ad- 
vantage of being able to mold the concrete into one solid mass^ 

58 



thus overcoming a very serious objection which marks the use of 
ordinary block stone masonry. 

In making concrete for arched sheeting, parapets, light v^alls, 
etc., the proportions used are one part of Portland cement, two parts 
of screenings and four of crushed stone. These proportions have 
been found to give the best results in work in which concrete is used. 



Advantage of Screening in Railway Construction. 



BY E. H. LEE. 
(Engineer for Chicago & Western Indiana Ry., and the Belt Railway of Chicago.) 

A discussion of the merits of concrete at this late day must neces- 
sarily follow a well-beaten trail, as most engineers now use con- 
crete in preference to stone for all heavy foundation construction, as 
well as abutment and retaining walls, arches, etc. In the elevation 
of the tracks of the Chicago & Western Indiana R. R. Co., in this 
city, required under the ordinances, approximately lOO miles of 
single track will be elevated before the work is completed. In con- 
nection with this work something like 200,000 cubic yards of concrete 
will be required. On that portion of the work between Seventy- 
third and Fifty-fifth street boulevard elevated during the past sea- 
son, approximately 16 miles of single track were put up, on which 
90,000 cubic yards of abutment and retaining wall concrete masonry 
have been placed. While the proportions have been varied to some 
extent, the mixture in general used on this work has been Portland 
cement one part, sand or screenings three parts, crushed stone six 
parts. 

The use of screenings was adopted only after extended experi- 
ments, which were begun something like five years ago, the results 
of these experiments showing that concrete made from screenings 
was as strong as that made by using topedo sand. As an outcome, 
whenever the relative prices of the materials have caused such use 
to seem desirable, we have substituted limestone screenings in place 
of sand. The walls which were thus completed two years ago have 
withstood weather conditions in satisfactory shape. 

The concrete work in connection with the elevation and depres- 
sion of the tracks of the various railroad companies which cross 
each other at Sixteenth street in this city — this work being carried 
on under the direction of Maj. G. W. Vaughn, engineer in charge — ■ 
is thought to have given a great impetus in the use of concrete in 
this vicinity. In that work the use of ordinary cut stone masonry 
would have been very difficult, if not practically impossible. The 
concrete was constructed with comparative ease, and with satisfac- 
tory results. The quantity used was perhaps at that time larger 
than that required in any other work of a similar character in 
Chicago, and the results have demonstrated that the confidence of 
the engineers who decided upon it was fully warranted. Something 
like 20,000 cubic yards was the amount used in connection with that 
work. 



The abutment and the retaining- walls constructed by the Chi- 
cago & Western Indiana R. R. Co. for its track elevation are of 
much the same general design and construction as used elsewhere. 
The retaining walls average about 17 feet in height from the bot- 
tom of the foundations. They are 2 feet thick at the top, and the 
base of the w^all on the top of the foundation is given a width equal 
to 50 per cent of the height. The footing is given a projection of 
12 inches on the back and 18 inches on the front. The design pro- 
vided for a wall having a battered back mstead of a step back, in the 
belief that the resultant line of pressure is practically equivalent in 
either case, the battered back being much easier to form. These de- 
tails are an old story, but they may be of some interest as being con- 
nected with the general elevation of the tracks of the various railroad 
companies entering Chicago. This work, taken altogether, is one of 
the greatest enterprises of its kind in the world. 



Concrete Locks on United States Canal at Hennepin. 



BY J. \V. PAGE, 
(Of Page & Shnable, Contractin}^ Kngiueers and Builders ) 

Some idea of the value wliicli experts for the Federal govern- 
ment place upon concrete may be learned from the fact that the 
thirty-two locks for the Hennepin canal, the most important work 
of the kind in this part of the country, are being constructed of 
this material. It goes without the saying that if the men charged 
with the responsibility of selecting the proper material for this 
work were not thoroughly satisfied that concrete is the best it would 
not be used. Of these thirty-two locks the firm of Page & Shnable 
is constructing eight. All are of crushed stone concrete and are 
marvels of solid building, intended to last for all time. 

The details of a single lock will serve as an illustration of the 
entire lot. I may say, by way of preface, that in preparing the 
concrete we use a machine of our own manufacture, the capacity 
of which is 250 cubic yards a day, a quantity which has never, I 
believe, been turned out before by any one machine. .All of the 
work, including the important item of mixing, is under the direct 
supervision of the United States engineers, headed by Captain Riche, 
U. S. A., and L. L. Wheeler, Ass't U. S. engineer. These men are 
naturally very particular, as their professional reputations are at 
stake, and this in army circles means much more than in the walks 
of civil life. These men are now convinced that the mixing ma- 
chine is far superior to the hand mix for several reasons, two of 
which are that it is practically impossible to get men to do it in- 
telligently with the rapidity required and for a price which will not 
put the contractor into bankruptcy. 

The w^alls and mitre sills of these locks are founded upon piling 
crossed with 10 by 10 timbers, which are in turn crossed by 6 by 
10 timbers, the centers being two feet. The excavation is three 

60 




CONCRETE LOCKS OX THE UNITED STATES CAXAL AT HENNEPIN. ILL. 



inches below the tops of the piles, and the concrete is laid from that 
point to the top of the timbers, which is 23 inches, the mixture 
being one part of cement, three of sand and six of crushed stone. 
Each lock is about 230 feet in length, and about 1,000 yards of 
concrete were placed in the sub-structure and from 2,500 to 3,000 
yards in the superstructure. The retaining walls above the founda- 
tions are built with a base 9 feet and 6 inches in width. At a dis- 
tance of 7 feet above there is a jog of 2 feet 9 inches, and 7 feet 
above that another jog of the same size, leaving the 7 feet of the 
top only 4 feet in thickness. The retaining walls are built in sec- 
tions of 22 feet, the work being done on alternate sections and the 
intervals filled later. Bulkheads are used and the joints arranged 
with a triangular key J^ of an inch on each plane. The locks when 
completed are of a far more substantial character than similar works 
of stone, and are impervious to the action of the water and the ele- 
ments. The gates arc swung above the mitre sills and back into 
openings made for them in the concrete construction. At one of 
the locks a slope paving for the approach was built of concrete a 
foot in thickness, and this plan will very likely be followed through- 
out the w^ork, although at first it was proposed to make the protec- 
tion of rubble. In this, as in other concrete work which we have 
done, crushed limestone has been used in preference to any other 
material as a base for the concrete. We have never used screen- 
ings thus far, but wc are now aware that they are equally as good 
and in many cases better than sand as a concrete mixture. This has 
been ascertained both by tests and actual experience. In the re- 
taining walls the cement is introduced in quantities of ii-io bar- 
rels to the vard of Portland and il^ of natural. 



Comparative Tests of Concretes Made With Lime- 
stone Screenings, Pit Sand and Gravel. \ ^^ 



BY G. J. GRIESENAUER. 
(Cement Kxpert and Tester for the C. M. & St. P. By.) 

Comparative tests made in the ce- 
ment testing laboratoryof theBridge 
and Building Departmentof the Chi- 
cago, Milwaukee & St. Paul Ry., un- 
der the direction of Engineer and 
Superintendent C. F. Loweth, M. A., 
Soc. C. E., indicate that limestone 
screenings are superior to either tor- 
pedo or pit sand in concrete work. 
While the number of tests is some- 
what limited, the results obtained 
are so uniformly and so decidedly 

^ ^ r^ in favor of screening-s that they de- 

G. J. Griesexauer. ^^ ^- 1 -1 ,• 

Cement Expert, c, M. & St. P. Rv. serve attention and consideration. 

62 




The first and second series of these tests were started a year 
ago, and that portion of the screenings which passed through a No. 
12 sieve and was held on a No. 40 sieve was used, the remainder 
being rejected. The result of this series is shown in Table i. Since 
that time other tests have been made, all the screenings which passsd 
a certain sieve being used instead of rejecting the fine portion. The 
superiority of the whole screenings (all the material that passed a 
given sieve) over the sized screenings is shown by a comparison 
of Tables i and 2. These tables also demonstrate the superiority of 
both classes of screenings to torpedo sand in tests made with the 
same cement and the same proportions of mixture. As the tests 
were distributed over a period of more than a year, a different lot 
of cement was used for almost every series of tests. The sand used 
was from the Hammond, 111., pit, this sand having shown the best 
results of any pit, beach or river sand that has been tested in this 
laboratory. The crushed limestone was from various quarries. 

Table i shows tests of crushed limestone screenings that passed 
a No. 12 sieve and were held on a No. 40 sieve. These tests average 
about 74 per cent, better than the comparative sand tests, and at the 
age of one year nearly 4 per cent, better than the neat cement tests. 
Both of these results are remarkable. Table 2 shows tests of 
crushed limestone screenings, which in all but one instance represent 
everything passing through the sieves, as indicated. These tests show 
that it is desirable to use the whole of the screenings. The i part 
of cement to 3 of screenings mortars average about 115 per cent, 
better than the i to 3 sand mortar. Even the i to 6 screenings 
mortars show an average of 22.9 per cent, greater strength than the 
I to 3 sand mortars. The i to 3 No. 4 screenings are about 23 per 
cent, better than the i to 3 No. 8 screenings. This table contains 
many remarkable comparisons and warrants considerable study. 
Table 3 shows tests of crushed limestone and crushed screenings. 
These tests confirm the conclusions reached from Tables i and 2, 
and emphasize the superior strength of limestone screenings over 
sand. Note in this table the great difference in the figure for lime- 
stone screenings and crushed gravel, and the slight difference in 
the figures for crushed gravel and sand. This table represents rather 
a limited number of tests. It cannot be considered as absolutely 
convincing, but is suggestive enough to have a bearing on the 
subject. 

These tests are suggestive in view of the thousands of car loads 
of limestone screenings that are separated from the crushed stone 
at the crusher mills and piled up as rejected waste, supposed to be 
valueless material. They also contradict reported tests of the in- 
ferior value of stone dust and screenings as compared to torpedo 
sand in concrete. In fact, they indicate value in limestone screen- 
ings over torpedo or pit sand such as was never dreamed of. 

As stated, the tests are limited in number, about 225 tests in all 
being included in the three tables. The great and uniform strength 
of the mixture made with limestone screenings as compared with the 
other mixtures surely has some bearing on the greater value of the 



OS 



screenings. After the briquettes of the different compositions were 
tested for tensile strength they were subjected to the steam and boil- 
ing tests, and proved entirely satisfactory. These tests are prelim- 
inary and other tests are under way. 

As shown in the tables, the proportions of the different mixtures 
were determined by volume and not by weight. The volume method 
for determining proportions of the mixture is preferred by the 
writer for the reason that the different relative weights of different 
limestone, sands and cements (which difference mav varv oreatlv) 
would change the intended proportions, and also for the reason that 
in regular concrete work the proportions are nearly always deter- 
mined by the volume method. 

The sand used should be clean, i. e., free (or nearly so) from 
loam or clay, and should be naturally clean rather than washed sand, 
because in washing some of the very fine particles (a valuable part) 
are almost sure to be lost unless special care is taken. The sand 
used in the accompanying tables contains less than i per cent, of 
substances soluble in water. 

The theory of the writer as to the caus^ of limestone screenings 
being superior to sand or crushed gravel is briefly this: (i) — The 
limestone is porous as compared to sand or gravel, therefore there 
is the possibility of its becoming saturated with the fluid mixture 
of cement and water. The smaller the particles of stone the more 
completely saturated will they become. This suggests a tendency 
of the mixture to become homogeneous in composition and simul- 
taneously homogeneous in strength to a greater degree than is pos- 
sible for a sand or other less porous material similarly mixed. (2) — 
The elements contained in limestone are solid forming or crystal- 
lizing elements. When these elements are attacked by the active 
crystallizing and solid forming elements of the cement they form 
a chemical union with the cement. The more complete the satura- 
tion the more complete will be the union ; thus the limestone and 
cement form an intermingled homogeneous mass. (3) — A mixture 
of cement and limestone screenings packs very closely, the particles 
being such as to fit themselves closely to one another, thus reducing 
the voids. 

To establish more closely and more firmly the exact value of the 
screenings of crushed limestone, and in what proportion this mate- 
rial should be used in concrete to give the best results, elaborate and 
careful comparative tests should be made by those interested in this 
line of work. 



64 



c 

s 

U 

c 
a 



o 


bfi 


^ 


c 




c 


M-i 


o; 


o 


V 






t/) 


u 


j::; 


in 


bx 


<i) 


c 


c 


V 


o 


in 








<D 


c 


> 


J 


.i_i 




03 
03 


N 


£ 


'U) 


o -u 


u 


c 




03 


1 


1 ■ 


1-H 


c 


, 


u 


o 




z 


(U 


V 


O 


Si 


c 

03 




V. 




O 




PLh 





•S)^U!U30.I0t^ 


-(< iC 






5 .^; 
r ^ 

- u 
E =^ 


•S.1UOA f 


i ^ 






■J^^A I 


CO t* 






•squiojM 9 


2 S 






•siiiuoiY ^, 








•sabq m 


^ 8 






sAbq Z 


^ CO 




Tensile Strentith in Pounds Per 
Square Inch. 


■SJH.^A 6 


- § - fe 

C5 O -f CO 
l^ CO '^ oo 


•-iHaA I 


S 1 5 i 


! ^ O C CO 

■sqniOH9 g § ^ K 


•squiOIV 8 


s s s ?^ 

Tf< ^ CO i> 


•S.^BQ 86 


^ i ^ g 


•S-VKQ L 


S 1 S i 


d 
o 

D 
N 


•pUBS 




XI 




•S3UIU99J3S 


^ ^ 
i 2 


Proportions 
by Volume. 


■pUHS 




CO 


•s^Suiuaaaos 


CO CO 






•JU9UI93 


_, ^ 

-H ^ ^ ^ 




2 

< 

t 1 

1 


tri or 

£ S 




3 
3 

re 
5 





65 



C 

a 



c 
a 

c 



V 

re 



n3 

u> 
ra 
O- 

E 

o 
■U 

I 
6 



a 



(J 



o ^ 

OS C 



c 

V 

en 
CJ 



llil 

t ■- ^ 

z. or. 


•pUB§ 


O X — (M :o =v — 

8 S S = ^' - ^ 






S3U!U89J.-)S 


i ^ i ^ H £ - 






■OX aAojs 


- - - 55 S S 1 






Aver- 
aye 
Per- 
cent- 
age. 


ssuiuaaaos 


182.7 
143.0 
105.6 
75.3 
49.2 
22.2 
126.6 
8.0 




-X 


•sq}uop^gl 


CO O 'l; -N Oi Oi OS i- '■ 

S ^ ^ $ S ^ ^ ?i 




1 ^ 


•sinuoK9 


139.4 
121.1 

55 . 5 

25.8 

106.9 

1().7 




- > 
r. v) 


•squioi^t: 


213.2 
182.5 
116.7 
84.8 
68.5 

132.7 
3.8 




iH 9 


•S.VBa 8S 


309.3 

142.0 

100.4 

51.0 

30.1 

12.8 

133.2 

10.2 




t ^ 


•S-iBQ i 


cc -s, X •^! — -s. ..■: -t 







= 




sqUJOj^Sl 


X 


i 


g 


i 


i 


s 


i 


1 


i 


X 


^ 


sqjuop^Q 


i 


H 


i 


i 


i 


g 




i 


i 


g 


r. 


si|iiioi^ i: 


i 


s 

i^ 


.s 


lO 


s 


g 


1 




ii 


i 


■7 


•sXea 82 


§ 


S 


i 


s 


1 


S 


2 




s 

»» 




H 


S^BQ i 


1 


fi 




i 


1 


»n 


1? 


S 


§ 


O 



pUBS 



5 |s;<u!u.-toaos 



X X X X X X 



•pUBS 



SXUIU09J0S 



f ift S) ec 



I I 



niaiuao 






o 

c § 
^ S 



ii o 

C ^ 

CD 

i; — 

> V 



u 

c 
a 



Percentage of Gravel Screenings 
Passing the Various Sieves. 


OO^OX 3A0IS 




If; 








oorox 3Aa!S 








Oo ox-^Aois 




2 ; 




•t? OX'^AOIS 




3C 

?5 






■fl ox 3A01S 




■M 






•8 -ox 3A0IS 




30 

3 






■f -ox 3A3IS 




o 

8 




Average 

Superiority 

to Sand. 


•sSu(ua3.iDS 




Percent- 
age of Su- 
periority 
of Screen- 
ings and 
Sand. 


•SABQ 8r. 


•^ If: 




•SABQ L 


ij -■ : : 


Tensile 
Strength in 

Pounds 

Per Square 

Inch. 


■sx\>a 8? 


ills 


■SABQ I 


1 i S i 


Size. 


•pUBS 






30 




■s.Suiuaa.TD§ 


X) 30 






11 
p 

I 


■pUBS 


: ec : 


•sSuiuaaaDS 


ec tc 




•U13UJ9J 


— — _ "^ 

Si 




< 
< 


y 

c 
c 


r 

> 


■y 

c 

£ 
E 


£ 


) 



67 



Irrigation and Power-Producing Plants in Concrete, 



BY THOMAS T. JOHNSTON, 
(Constructing and Cousultins: Engineer, Chicago.) 

One of the most interesting works in concrete — a material which 
I have used since 1876 — is the irrigation aqueduct over the Pecos 
river and valley in Xew Mexico. Placed upon an arch construction 
of concrete is a flume, 20x13 feet, which carries 1,500 cubic feet of 
water per second between its concrete walls. It is not alone because 
of the strength, durability and utility of the work that it is pecu- 
liarly interesting, as the entire structure, which is 500 feet in length, 
cost only $45,000, including all materials and services. It has been 
in operation for a year, has given complete satisfaction, and can 
never be subjected to tests that will overtax its strength. This struc- 
ture was built upon four arches, each with a span of 100 feet and 
a rise of 25 feet. The height of the work is 60 feet, and it required 
exactly 5,400 yards of concrete, the same number of barrels of ce- 
ment being used. The foundation for the arches is upon the con- 
glomerate rock of the river bed, and the piers are built 8x25 feet in 
dimension on the ground. The base of the foundation is calculated 
to withstand a pressure of 200 jwunds to the square inch. There 
is no reinforcement in the structure, excepting the iron used as 
forms, and in the superstructure where the metal is embedded in 
the concrete at intervals of four feet. The abutments for the work 
are 25x32 feet. It was out of the question to get crushed limestone 
for this work, and as a substitute a hard bedrock, containing about 
the proper amount of sharp sand, was quarried and crushed on the 
ground, and this, with the screenings, was used in the making of 
the concrete. A mixer, of the Page & Shnable design, was employed 
and the concrete mixture hauled in batches of three-quarters of a 
vard in dump cars elevated above the work. In this manner an 
average of 90 yards was laid daily, the cost of forms and centering 
being about $1 per cubic yard of concrete. The armoring of the 
four sides of the flume consists of 16,000 lineal feet of 50 pound 
"T" rails, with ends bent at an angle of 90 degrees, and placed 4 
feet apart, horizontally and vertically. With this iron work it was 
found that a concrete wall only two feet thick at the bottom could 
safely oppose a 16-foot wall of water. This construction at Pecos 
was an innovation, but it has been so successful that other concrete 
flumes have been carried across valleys and river beds on the same 
plan, and success has been universal. 

At Swan Falls, on the Snake river in Idaho, a complete power 
plant has been built of concrete for furnishing electric power to 
Silver City, which is up in the mountains 25 miles away. The dam, 
power house and wheel compartment are all of crushed stone con- 
crete. The dam, which is 350 feet across and sustains an enor- 
mous hydraulic pressure, is only 3 feet in thickness and is without 
reinforcement of any kind. The power house was erected w4th 



iMif^m- 








^ 




IRRIGATION AQUEDUCT OVER PECOS VALLEY. NEW MEXICO. 
(Built entirely of Concrete. Lower view shows interior of water flume.) 



accommodation for four water wheels, and terminates the dam at 
the east end. It is a structure 70 feet high, with the generators on the 
second floor above the wheels. It is entirely of concrete laid on the 
block plan. The arches for the support of the floors are also of 
concrete and are without reinforcement. They not only hold up 
the floors but serve as a foundation as well for the heavy generators 
which develop 2,800 horse power. The dam was constructed by the 
use of coffer-dams, the foundations being laid on the bedrock of the 
river. The base is 5 feet thick, and the walls extend upward 35 
feet. On the lower side of the dam there are 5-foot buttresses 
bracing the wall at intervals of about 20 feet for the entire length 
of the structure. The concrete was made with crushed stone quar- 
ried on the ground, and the mixture was of medium richness. It 
was made in sections in the ct)ffcr-(lams. which were floated into the 
river and sunk at the site of the work after being anchored. This 
plant has been a source of great pndc and j)rofit to its ])romoters. 
furnishing both electric power and light to Silver City. Although 
absolutely without reinforcement it is ami)ly strong to hold all the 
water furnished 1)\ tlie river, and no detlection has l)een detected 
notwithstanding the fact that the water is im])ounded for three 
or four miles back, and at some ])oints is three-(|uarters of a mile 
wide. 

My latest work of this nature is the C( instruction of a ])Ower 
hotise at the ( )li\(.r Plow Works in South Wvud, Ind. This build- 
ing is entirely of concrete with the exce])tion of the roof, which is 
of tile, this latter substitution bring made with a view to avoiding 
condensation on the ceiling. The building is 275x40 feet on the 
ground, and has one story of 20 feet. A concrete platform was 
laid on the cla\- and hard-j)an and T.400 feet of retaining walls built 
up from it. The wheel bays and waterways are of concrete, and 
the side walls of the structure are of concrete blocks. Between 
6.000 and 7.000 \ar(ls of crushed stone concrete were used in the 
platform, retaining walls, waterways, etc.. and with the single ex- 
ception of the roof the structure is solely of that material. 



Defects of Sand as a Concrete Ingredient. 



BY ]]. J. KELLY. 
(Concrete Expert and Builder for the Knickerbocker Roofing Company.) 

After a number of vears of experience with concrete work, 
during which I have used stone, sand, gravel and screenings, I 
have become thoroughly convinced, and I think with ample reason, 
that crushed stone, screenings and cement makes the most valuable 
and durable mixture. Except in cases where the use of gravel is 
specified by the architect or owner. I always give preference to 
stone, because it developes into a stronger concrete, and there are 

70 




CONCRETE DAM AND WATER GATES ON THE SNAKE RIVER, 
AT SWAN FALLS, IDAHO. 



chemical causes which encourage a more rapid and perfect adhe- 
sion than can be obtained with gravel. Some of the most interest- 
ing observations I have made have been with regard to sand and 
screenings. My work is to a large extent of a nature which requires 
hard surfaces and smooth finishes. For the hard surfaces the tor- 
pedo sand is without comparison ; heavy traffic will not wear it 
down. The block with this finish will last indefinitely, so far as wear 
is concerned. But there is another side to the subject. Washed 
sand is perfect. The trouble is that it is practically impossible to 
secure washed sand. It is very difficult to satisfy even the best of 
experts on this point except by exhaustive tests. A streak of loam 
may exist in a load of sand and escape detection. As a rule there is 
a great deal of it. The loam is taken from the pits' with the sand 
and is so buried and mixed that no one can see it. This mixture 
is a dangerous thing. I have found that th^^ presence of loam 
.prevents the thorough adhesion of the cement and sand. It may 
ie a very small proportioir of loam, hut the damage will be done 
and you cannot detect it until the work is completed. Then in a 
short time xou will get evidence of trouble. Cement and loam 
will not work together; thi're is no chemical al^nity between these 
substances. Disintegration is the" result, and we all know what this 
means. 

Screenings, on the other hand, are liglit in color, and if anything 
of a foreign nature becomes mixed with them it is easily seen with 
the naked eye. For ensuring a ]3crfect concrete it would be dif^- 
cult to improve upon screenings, this assertion being made par- 
ticularly in view of the conditions existing in ini washed sand. Tak- 
ing everything into consideration, screenings are safer and better. 
A flaw, or break, or crumbling in concrete will cost more to repair 
than the investment will justify, and for tliis reason we should make 
sure of having the best. 

We have just completed the largest piece of concrete work the 
Board of Education has ever ordered in Chicago. It consists of a 
yard for the Burr school at Marshfield avenue, Waubansee street, 
and Ashland avenue. The job cost i{>io,OD0, and necessitated the 
walling up of the entire school yard, which is ])aved with brick. 
In this work there are 800 feet of retaining wall yYz feet in height, 
6 feet above the ground, and 2^^! feet thick. The walks are 14 
feet wide, and a driveway to the front entrance of the school is 32 
feet in width. The mixture used in this construction was 
^- Cement, one part : sand, three parts : crushed stone, four parts. 

There is one inch of finish on the wall and walks which is about 
as artistic a thing as can be devised. This finish was made of equal 
parts of cement and sand. The yard was six feet below the grade 
of the sidewalk, the street grade having been raised after the school 
buildings were erected, and when new walks became necessary we 
found that it would be imperative to build retaining walls to keep 
the sidewalks in the streets, where they belong. There is an old 
brick and stone wall at one end of the vard, and the new concrete 



work joins it. People interested in works of this nature should 
make a comparative inspection of the two methods of construction. 

This work was delayed and is not as satisfactory as one would 
wish on account of the difficulty in procuring clean sand. The 
specifications of the Board of Education called for sand, and pre- 
vented our using- screenings. We were, therefore, compelled to use 
sand against our judgment or desire. 



Concrete the Rational Setting for Steel, 



BY CHARLES S. FROST, 
(Of the firm of Frost & Granger, Architects.) 

Concrete used in combination with steel is admittedly the best 
form of construction. That it is far better than natural stone is 
acknowledged by all modern engineers ; in fact, men of experience 
decline to make use of natural stone in this condition. By com- 
bining concrete with steel one product offsets the defects of the 
other. Each is strong where the other is weak, and by joining the 
two we get the acme of strength. It is for this reason that con- 
crete is now almost universally employed in connection with the 
steel work in all our great modern buildings, and even though in 
some instances natural stone would not increase the cost of con- 
struction conscientious engineers would not revert to it. I do not 
believe that real proficiency in the handling of concrete without steel 
reinforcement for upper work has yet been reached, and for this 
reason some men are still timid about having recourse to it in this 
way. Personally I would employ concrete even more extensively 
than I do if it were not for this feeling, as I have the utmost confi- 
dence in it. In France, especially, the use of concrete has reached 
a high stage of development, and French artisans use it without 
a tinge of the feeling which still obtains in some quarters in this 
country. The main trouble here is that there is a prevalent idea 
that the art of concrete making and its practical application rest 
too much upon the uncertainty of human nature ; in other words, 
that some workman may err and that his mistakes or blunders may 
result in large losses. This danger is obviated, of course, if we 
assume that the engineer in charge of the work is perfect in his 
comprehension on the subject, and that the workmen under him 
perform their tasks with scrupulous fidelity. When these condi- 
tions are had here, as they now are abroad, the use of concrete 
will become universal. 

One of the most extensive pieces of concrete work in the way of 
foundations being done in Chicago this season are those for the 
general office building of the Chicago & North-Western Railway 
at Jackson boulevard and Franklin street. Here fifty piers, upon 
which the steel frame of the big structure will rest, are being built 
upward from the solid rock which is about lOO feet below city 



'datum. In general characteristics these piers differ Httle from 
those generally employed for similar purposes in this city. The 
work is of interest almost wholly as illustrating the advantages 
of concrete construction. In this particular instance it would be a 
practical impossibility to build stone piers from the bed-rock, and 
•even if it could be done they would be no better and probably not 
as good as the concrete, while the latter are nuich less expensive. 
In all of this work crushed limestone is used. 

When the question of the concrete mix for the La Salle street 
station arose, I must admit that 1 was skeptical regarding the utility 
of employing the screenings which came from the crushing of the 
stone of which the old buildings were constructed. At that time 
I believed that the contention of the railway engineers to the effect 
that the mixture would not be durable, or i)ossess the necessary 
strength, was correct. Laboratcry and ])racticcd tests of the con- 
•crete made with these screenings, liowever. convinced me it was a 
•superior article, and it was rvenlually used in the foundation work, 
some sand 1)i'ing acUlecL 



Concrete as Utilized by International Harvester Co. 




BY W. D. PRICE. 

Snperinteiidt'iit of Construction for the McConnick Division. 

For eight or nine years past the 
McCormick Harvester Company has 
been using crushed stone concrete in 
a general way, and for the last four 
>'c'ars this material has been em- 
ployed exclusively for foundation 
work and floors. In this time I have 
not used a single dimension stone in 
the foundation work, and when it is 
taken into consideration that during 
the tenure of my office I have built 
about 90 per cent of the structures 
comprising this immense group, it can 
w D Price t)e easily understood what we think 

•Supt. of Construction. McCormick of Concrete and the results obtained 

Harvester Co. ^^^^ j^S ^^^Q 

In all the various departments of the ^IcCormick works concrete 
is a general article. Wt use it for the bases for the heavy machin- 
ery, such as steam trip hammers, for floors which have to support 
■extraordinarily heavy weights, for foundations of all kinds, for 
:shipping platforms, walks, and in fact every conceivable place in 
which we require durability, freedom from weather effects and un- 
usual weight-sustaining power. 

While concrete has been thus generally employed for a long 
time, it is ojily recently, speaking in a comparative sense, that I 

74 



have tested its merits to my comi)lete satisfaction in the matter of 
floors, of whicli we now have two exceedingly good specimens. Be- 
fore placing the first of these floors in the press room I made a 
crucial test of the material in the yard. Upon four tiers of brick 
was laid a section of crushed stone concrete 6 inches thick and i8 
by 20 feet square. Four concrete beams served as the sustaining 
bases. These were 18 inches in height, and the reinforcement in 
the concrete flooring was attached to them. Upon this structure 
was placed an evenly distributed w^eight of 350 pounds to the square 
foot, without causing a deflection. Unfortunately the test was not 
completed. In attempting to concentrate the weight to the center 
an accident occurred which was not in anv wav due to the concrete. 




TEST PLATFORM OF CONCRETE ERECTED AT McCORMICK HARVESTER WORKS. 



One of the piers had been unknowingly built over a bit of soft 
ground and wdien the extra weight was added the pier foundation 
sank a couple of inches and let the corner dow^n. I never went 
any further with the test as I was amply satisfied as to the weight- 
sustaining and other merits of the concrete itself. 

When the question of building an absolutely fire-proof paint- 
mill building came up we decided unhesitatingly upon installing a 
concrete floor. It was arranged to build this with a 14-foot clear 
span, the "I" beams being that distance apart, with concrete beams 
at the same interval in the other direction. This floor was built of 
6 inches of crushed stone concrete. It was constructed wath heavy 
fence wire as a reinforcement, doubled so that the outside ends 



would stand 6 inches apart. A maple lioor was placed over the 
concrete after the false work was taken away, and we decided that 
the safety weight-sustaining strength was 350 pounds to the square 
foot. Some time later, without my knowledge, workmen placed 
upon this floor, which is on the second story, a number of large 
barrels of mineral paint, one on top of another, until they had 
massed a total of 1,000 pounds to the square foot. Tnis- immense 
strain caused a deflection of about 5-7 of an inch, and we later 
placed concrete beam supports under the deflected portion. This 
same floor, without any further assistance, is now carrying a con- 
stant weight of 350 pounds to the square foot and has been in use 
two years, giving complete satisfaction. 

In the press room we have another second-story floor of con- 
crete which is worth more than passing notice. Here the dimen- 
sions are 40 by 320 feet and the entire space is used for the storing 
of heavy machinery. The concrete mixture was about the same as 
that used for the floors of the paint mill. In this storage floor we 
/lave spans every 16 feet, with concrete cross beams at 6-foot inter- 
vals. Wire and rods which hook over the "I" beams are also util- 
ized. This floor we have tested to a weight of 650 pounds to the 
square foot, and I do not hesitate to assert that it would carry fully 
1,000 pounds without aj^j^rcciablc deflection, and even more than 
that. 

Coming to the matter of concrete foundations, our Xo. 5 ware- 
house is a seven-story and basement building 83 feet wide and 501 
feet long. The interior columns, 109 in number, are supported on 
concrete piers without the use of dimension stone. Although these 
piers carry a weight of 358 tons each, there are no signs of settle- 
ment or give of any kind. The iron columns in the basement and 
first story of this building are protected with crushed stone concrete. 
In all our new buildings the foundations are of concrete. These 
are much easier and cheaper to build than those of natural stone or 
other material, and last longer. The concrete is a great deal more 
easy to handle and has numerous other obvious advantages. 

We have had great difficulty in the past with our wooden plat- 
forms- on account of the supports giving way and the timber and 
floors rotting out. During the past year we have built a platform 
along our new press room, 14 feet by 310 feet, entirely of concrete. 
On this platform we receive all our steel for blacksmith shop and 
forge work. Around our new warehouse we have erected a plat- 
form with concrete curb walls and concrete floor with strips worked 
into the concrete, and a wood floor instead of cement finish. This- 
substantial platform is 20 feet wide and 1,208 feet long. The con- 
crete mixture for this platform contains six parts of crushed stone 
and has been found ideal for that purpose. In the foundation and 
platform work one-inch stone is used, but in the floors the size is 
restricted to one-half-inch. 

Experience has taught us more than experiments. We watch 
the results and base future operations upon them. For instance, I 
am awaiting the necessity for another platform shelter. The ones 



now in use are of galvanized iron and steel. The next will be of 
concrete. I have inspected works upon which these concrete roofs, 
are placed and can readily see the value of them. The use of gravel 
and cinders for a base for concrete is a subject to which I have 
o^iven much consideration, but the former I have found does not 
bring about the homogeneous results which limestone will. There 
is no doubt in my mind but that crushed stone will make a far 
more substantial mixture. The cinder concrete has not the body 
of that made with stone. In 1897 I put down a concrete floor in 
one of our large buildings in which I used screenings exclusively 
in place of torpedo sand. This floor has had the hardest kind of 
usage, but is in excellent shape today. 



Concrete Foundation Piers Highest Form of Perfection, 



BY J. G. GIAVER, 
(Expert in charge of Foundation Work for D. H. Burnham & Co., Chicago.) 

Upon eighty concrete piers, which were constructed on the basis, 
of sustaining 44,000 pounds to the square foot, rests one of the 
most massive buildings in Chicago — the Marshall Field retail store,, 
which covers an entire block at State and Randolph streets. It may 
not be out of place to state here that this result would have been 
impracticable by any other method. 

These concrete foundations are the most shining example of 
true economy in this line as at the present day perfected and under- 
stood. It is no exaggeration to say that no other practical form 
could have been substituted for this kind of a structure. The same 
holds good as regards the new First National bank building, a 
considerable section of which has been completed on Monroe street. 
Underneath this latter structure especially is a foundation of con- 
crete which, considering the nature of Chicago soil and the difh- 
culties it presents, has no equal in the world. Properly speaking 
these mammoth structures and the new Railway Exchange building 
as well rest upon the solid rock. This was made possible only by 
the employment of concrete piers, in the construction of which 
original and novel methods were introduced. 

For many years the aim of Chicago architects and builders has 
been to secure a foundation which would adequately support the 
great weight of modern office structures. To those acquainted 
w4th the peculiar nature of the soil in the business district this has. 
ever been a perplexing problem. A large part of down-town Chi- 
cago is underlaid by a bog or m.orass. At first builders essayed to- 
overcome this by driving piles as a support for the foundations, but 
this was found expensive and unsatisfactory. Then came the era 
of spreading a solid mass of iron rails embedded in cement over the 
spiles, only to find in the end that there were fatal objections be- 
cause of the uneven settling. With the advent of ingenious ma- 



chinery which makes possible the sinking of wells clear through 
to bedrock the concrete pier has been introduced, and with it has 
come an acceptable solution of the annoying problem. These wells, 
often improperly referred to as caissons, are excavated to the rock 
and in the holes thus made the concrete piers are built, securing a 
solid and unyielding foundation, the weight-sustaining power of 
which is limited only by the size and number of the piers them- 
selves. The dimensions and form of the wells vary according to the 
conditions to be overcome. At the First National bank building, 
for instance, all the wells are perpendicular — the same size from 
top to bottom — and arc sunk to a unift^rm depth of 102 feet. There 
are seventy odd of the pillars, a little over sixty of them being 5 
feet 8 inches in diameter and twelve being g feet 8 inches. They 
all stand squarely upon bedrock and simjily hll the ])lace of great 
stilts to hold the building above the rock formation. 

In the Marshall Field and Railway Fxchange buildings the 
pillars are of bell shape. They extend to a depth of 90 feet. Two 
sizes are employed. Those which are 5 feet 8 inches at the top con- 
tinue at that size until within fourteen feet of the bottom, when 
they broaden out to 14 feet, thus insuring a greater sustaining 
power. In the 9 feet 8 inch j^illars the bell extension is 22 feet. 
These 90-foot pillars all rest u])on hardpan. While it was possible 
to strike bedrock at 102 feet on the bank building site, at the other 
structures it would have been necessary to go down at least 130, 
and ])erhaps 140 feet, as they are much nearer the lake, towards 
which the l)e(lrock dips. In the sinking of the wells but little water 
was encountered and in some instances we had to force water into 
the holes to facilitate the excavating, particularly in the vicinity of 
the liard])an. 

All the wells were excavated by machinery and when the holes 
were made the machines were removed and tlie ])latforms for the 
mixing of the concrete put up. In every instance the mix was the 
same, being one part of cement, two of sand and four of crushed 
limestone. This amount of cement and sand is considered by many 
experts to be excessive in comparison to the proportion of crushed 
stone, but in this case, where the results were so important, we did 
not feel like taking any possible chances. Workmen are not al- 
ways careful in looking after the exact proportions of materials 
and it was thought better to make the mixture more expensive than 
to take any risks, as a defective pillar would involve the loss of a 
large amount of money and perhaps endanger the entire structure. 
When we were ready to begin the concrete work eight-inch pipe 
chutes were lowered to the bottom level of each well and the con- 
crete mixture poured through them. In this way the mixture was 
kept together on its descent and at the bottom became compact and 
well tamped by the force of the drop. These pipe chutes weic 
movable and we w^ere thus able to lay the concrete evenly. It too^ 
about seven days to fill the 5 feet 8 inch wells and about nine days 
for those of 9 feet 8 inch size. W> put in something like 1.5 yards 
of concrete to the running foot of the smaller pillars, and by the 

78 



time each pillar was completed the mass at the bottom had set. 
This result was obtained bv using the crushed limestone mix, the 
product being- niuch more homogeneous than that obtained with 
other materials. 

There are no reinforcement rods or other iron work in the 
concrete piers we have constructed. We aim to have each pillar 
large enough to sustain the weight of sides and top at the base of 
the pillar. The weight at the base of the columns in excess of the 
weight of the superstructure is about four tons or 9,000 pounds to 
the square foot. In these masses of indestructible concrete there 
are probably from 22,000 to 25,000 yards, and the material is per- 
fect for the purposes intended. It must be when we stop to con- 
sider that it is under a total pressure of 44,000 pounds to the square 
foot, which means more than 300 pounds to the square inch at the 
base of the column. Care in construction is the only absolute ne- 
cessity wdien concrete is employed. 

To sum up I will say that these are the most satisfactory results 
with foundations that it is possible to secure. As to the use of 
•other materials in the instances of these three buildings, I am posi- 
tive it would have been impossible to get anything like the same 
effects. 

So far as "armor" concrete is concerned we have made little 
use of it, being as yet unacquainted with its real properties. I am 
waiting with considerable curiosity to ascertain wdiat part this con- 
crete played in the Baltimore fire and believe there is an instruct- 
ive study in this line for all builders in the detailed reports of the 
recent conflagration in that city. 



Superior Strength of Limestone Screenings to 

Sand. 



(Oflficial Report by the Chicago Testing I^aboratory.) 

The following tables are reproduced from official reports of 
tests made by the Chicago Testing Laboratory, which makes a 
specialty of investigating cement and concrete materials for archi- 
tects, builders, contractors and owners. In the winter of 1902 Mr. 
P. C. ]\IcArdle, the managing director of the laboratory, obtained 
in an impartial manner representative samples of high-grade Port- 
land cement, torpedo sand and limestone screenings. From these 
samples concrete was made according to three different formulas. 
The first was composed entirely of cement, the second of cement 
and screenings in the proportions of one to three, while the third 
■consisted of cement and torpedo sand in the same amounts. The 
cubes thus made were subjected to tests for tensile strength at 
varying periods of three, six and twelve months. The results are 
•.shown in the appended tables : 



TENSILE STRENGTH AT THREE MONTHS. 







TD . 


^ 


_c 


G J5 


u 


. u 


cc U 


c 


^^ c 


C/3 C 










c 


. 


■7: <U 


ment, 
:reeni 
er S(\ 


ment, 
orped 
er Sq 


^ s-o 




,0; ^ (1. 


S S 5 


rt rt 2 


^ ^ § 


z u ew 


« roO. 


- coCIh 


670 


300 


285 


600 


360 


325 


610 


340 


330 


675 


370 


320 


665 


340 


315 


Average.. 644 


342 


315 



TENSILE STRKN(;TH AT SL\ MONTHS. 







'6 




- 


j= 








t/5 ii 


C/3 ^ 




— 


tc - 


'- 






ment, 
reeni 
er Sq. 


iient, 
orpec 
er vSq. 




eat Port 
ement. 
ounds P 


Part Ce 
Parts Sc 
ounds P 


Part Ce 
Parts T 
ounds P 




Z U :i. 


- r^, C- 


- -^ 




572 


420 


312 




672 


447 


344 




573 


411 


358 




574 


350 


395 




610 


448 


304 




Average. .600 


415 


343 





80 



TENSILE STRENGTH AT TWELVE MONTHS. 







t: . 


— 


^ 


G ^ 


o 


• u 


a! U 


G 


Kn C 


CO c 










G 


. 


1 ^ 


g"'£c^ 
oj 33 ^ 




■— ; <v 


S M <^ 


c <u 


t: Oh 




OJ H ^ 

^^^ 


rt B 3 

aj (U o 


03 rt S 


c« 03 q 


!Z U Ci-( 


« rO&H 


^ ropH 


520 


458 


410 


540 


481 


381 


640 


471 


370 


635 


453 


403 


632 


520 


408 


Average.. 593 


477 


394 



(Signed), Chicago Testing Laboratory, 

Per P. C. McArdle. 

It was a foregone conclusion, of course, that the concrete made 
with neat cement would give the largest percentage of strength, 
and the figures of this result are valuable only for the purpose of 
•comparison, the initial cost of neat cement concrete making its gen- 
eral employment impracticable. The results obtained with this 
mixture, however, afford a basis upon which to compute the rela- 
tive value of the other mixes. The tables show that the average 
tensile strength of the cement and screenings mix at the three 
months period was 342 pounds to the square inch, as against 315 
for the cement and sand mix. And in this connection it should be 
remembered that the best quality of clean torpedo sand was used. 
At the six months period the cement and screenings concrete had 
an average strength of 415 pounds, wdiile that of the cement and 
sand product was only 343. When tested at the final period of 
twelve months the relative strength was 477 pounds against 394. 
Thus we see that not only was the cement-screenings concrete 
stronger at the beginning of the tests, but there was a very appre- 
•ciable increase in strength as the material aged. At three months, 
for instance, the average strength in favor of cement and screen- 
ings was 27 pounds to the square inch ; at six months this average 
had grown to ^2 pounds, while at twelve months it was 83. This 
supports the general contention of intelligent builders that the eco- 
nomical advantages of concrete made with cement and screenings 
^become more apparent with the passing of time, every year adding 
to its worth by increasing its solidity and strength. 



81 



Progress in Stone Concrete Masonry, 



BY JOHN DEAN. 

(Member of the American Railway Engineers' Maintenance of Way Association. Extract 
from paper read before the Engineers' Club of St. Louis, Mo., Feb. 4, 1903.) 

No branch of engineering has made greater strides, or shown 
more rapid development, than concrete masonry construction during- 
the past decade. Up to a very recent date most engineers had but 
hazy ideas of the proper uses of concrete, or of the correct propor- 
tions for mixing a concrete for any given purpose, and many even 
entertained grave suspicions of the vahie of concrete itself. Nowa- 
days this is all changed, and the places in which stone concrete ma- 
sonry is used in lieu of cut stone masonry is legion. 

There have been many causes that have led to this result, but 
two of the main reasons are, the improvement of the quality of our 
American Portland cements, with the great lessening of the cost of 
the same, and the developing of stone-crushing machinery as it is 
found in our modern crushing plants of to-day. Stone concrete can 
be found oxer a thousand years old, in good condition, in the ruins 
of the ancient castles and various great buildings of the old workU 
but the builders of these days lacked the cements we now ])0ssess. 
With the acknowledged improvements in the manufacture of Port- 
fand cements has come an apj)reciation among engineers of the value 
of concrete, and as a result numerous experiments and tests have 
been made, and these tests have shown that cement concrete, ])rop- 
erly ])repare(l and ])laced, is one of the most reliable materials that 
the engineer has at his disposal. 

The ])ractical reconstruction of most of the leading railroads of 
this country during the last few years has called for stronger and 
more permanent structures to replace old ones which had been con- 
sidered heavy enough at the time of their erection, and the question 
naturally arose as to the proper material out of which these were 
to be constructed. The cost of many of these structures would have 
been prohibitory if cut stone masonry had been the sole choice, but 
the lower cost of good concrete masonry enabled them to be carried 
out. 

A good quality of stone which will not succumb to the ravages 
of our climate is hard to find, and when found is a very expensive 
luxury in the ^Middle \\>st, but a stone that makes a lasting con- 
crete when thoroughly imbedded in a matrix of Portland cement 
mortar can be obtained in abundance, and at a reasonable cost, form- 
ing a structure that is practically indestructible. Here, then, was 
the solution of the problem, and as a consequence we find the con- 
sumption of Portland cement has increased over 500 per cent, in the 
past ten years, while at the same time the cost has decreased con- 
siderably. 

On the work on which the writer has been engaged the past five 
years, the double tracking of the Grand Trunk Railway, and on 

82 



which about 30,000 barrels of cement have been used, the cost of 
cut stone masonry and stone concrete masonry was compared by 
Mr. H. A. Woods, Chief Engineer of Construction, when preparing- 
the estimates, and it was found that the whole cost of the concrete 
masonry complete in the structure was about equal to the cost of a 
good stone on the cars, so there was no hesitation as to the choice. 

One of the great drawbacks to the use of cut stone masonry on 
a road in operation is the need of heavy derricks and machinery, 
which are necessary to the handling of the large blocks of stone,, 
and in consequence are a source of danger, as well as delay to traf- 
fic, whereas in the case of concrete masonry all the necessary ma- 
chinery, tools and forms, are entirely clear of the track, and need in 
no case interfere with the traffic. 

Again, it requires skilled workmen to cut and lay stone masonry,. 
and as this class of labor is expensive, and in the building season 
limited in quantity, and sometimes unreliable, a certain limit is set 
on the amount of work that can be done in a reasonable time, and 
this constitutes a very serious objection to stone masonry, where 
speed is a desideratum. On the contrary, the ordinary unskilled 
labor of the country, under the guidance of a competent foreman, is 
perfectly sufficient for building the largest and most elaborate con- 
crete masonry structures. 

We have yet much to learn about concrete masonry construction 
and its capabilities, and feel that there is a very large field for in- 
vestigation and experiment, both for the practicing engineer and the 
laboratory student, concerning the varied conditions and loads which 
existing structures are subjected to, and will endure in their every- 
day life. For the present-day engineers, the places in which con- 
crete is a suitable material, and often the only practically available 
material, are almost innumerable ; among them may be mentioned 
bridge piers, abutments, foundations, culverts, arch masonry, retain- 
ing walls, pedestals, copings, cylinder piers, dams, lock masonry,, 
dock walls, footings for iron columns, concrete facing to repair old 
masonry, concrete backing to masonry, ends to iron culvert pipe^ 
foundations for engines, machinery, turntables, pits, water tanks,, 
etc. ; foundations for buildings, walls of buildings sometimes solid 
and sometimes formed of hollow blocks, concrete floors and side- 
walks, tanks, vats and grain elevators. High chimneys are built of 
reinforced concrete, and every day seems to show a new use for this 
material, which proves to be adapted for all kinds of purposes. 

The ideal concrete would be an homogeneous mass of broken 
stone cemented together by just enough cement mortar to fill all the 
voids in the stone, the mortar forming a perfect matrix ; but in 
actual work this cannot be attained, so we must allow an excess of 
matrix, or enough cement mortar to completely fill all the voids 
where we have large bodies of concrete to place with the ordinary 
labor employed. A great number of experiments have been made 
to determine the voids in crushed stone, which show from 45 to 50 
per cent., varying with the size of the stone. The writer has used 
the following proportions for a good many years, deduced from the 



above, which leaves a sufficient margin of excess of mortar to be 
practicable for every-day use : 

I part cement, 2 parts sand, and 4 parts crushed stone for arch 
rings and similar work ; i part cement, 3 parts sand, 5 parts crushed 
stone for all exposed masonry, and i part cement, 5 parts sand, 9 
parts crushed stone for large masses of masonry under ground 
where not subject to abrasion of water. 

The stone used for concrete should be as hard, durable and an- 
gular as possible. No stone to be used which exceeds two inches 
in its largest dimension, all flat stone to be rejected. Experiments 
have proven that angular forms give a greater surface for the ad- 
hesion of the mortar in proportion to volume, at the sanie time leav- 
ing less voids to be filled with the mortar. By using what is known 
as crusher run of stone, with the dust screened out, we ol)tain all 
the various sizes of stone, which will, in placing and ramming into 
position, need the least jDercentage of mortar to fill the voids, and 
at the same time make the most homogeneous and C(Mn])act mass of 
concrete. 

Another question, as to which i)ractice has changed in the last 
two or three years, is the proportion of water necessary to make 
good concrete. It is now conceded that a wet mixture is better for 
all purposes, as it docs nc^t require such heavv tamping to make a 
comjxact mass. 

There have been latterly some interesting experiments made with 
fine limestone screenings as a substitute for sand in making con- 
crete, which show very good results : llie writer used the screenings 
for coating over an arch lately with juM-fect success. 

In conclusion, concrete masonry has come to fill such a large 
part in the modern engineer's practice that we must all learn the vast 
potentialities of the material. The writer has inspected and built 
a great number of concrete structures within the past decade, but 
has never seen a failure, where the same was well designed or built. 
There have been failures, but they were the result of faulty design 
or poor workmanshij). 



Notk: Since the above was written the Baltimore fire has shown that stone concrete 
masonry is the best resistant of fire, as the concrete there stood the most intense heat without 
failure, while terra cotta, wrought and cast iron, marble and stone crumbled away in the 
same temperature. 



84 



First All-Concrete Building in Chicago. 



BY E. M. CAMP. 

(Of IMnrphy & Camp, Architects, Chicago.) 

There is now in process of erection at Michigan avenue and 
Forty-ninth street, in this city, a building to which may be rightly 
awarded the distinction of being the first all-concrete structure of its 
kind in Chicago. In my opinion it marks the beginning of an era 
of concrete construction which is of vast importance to everybody 
interested in the welfare and advancement of the city, and especially 
to property owners and taxpayers. While this is my earnest belief 
I deem it only fair to state plainly that there are defects in this par- 
ticular structure which will be apparent. even to the casual observer, 
and which will undoubtedly be magnified and distorted by those 
opposed to this method of construction. These defects, however, 
are really of minor character and do not aftect the solidity or actual 
worth of the building. They are due. solely to the fact that one of 
the ow^ners of the property, a man intensely interested in concrete, 
but who has never had any experience in construction, insisted upon 
taking direct charge of the erection of the structure instead of 
entrusting it to some practical builder. This was a laudable ambition 
on his part, but has naturally resulted in errors which under other 
conditions would have been avoided. Constructed of almost any 
other material under the same circumstances it is almost a certainty 
that the structure would have collapsed. This in itself is a strong 
endorsement of the merits of concrete as a building material, and 
demonstrates that reasonably good results may be obtained even 
when used by men wdio are not conversant with the vital principals 
of construction. 

This building, which is 150x58 feet in size, three stories in height, 
and intended for apartment purposes, is constructed on the mono- 
lithic plan — that is all the exterior walls are of one solid mass instead 
of in blocks. To relieve the monotony of appearance the concrete has 
been ''beaded" in molding so as to give a block effect. The concrete 
is made of cement and crushed stone (screenings) with the excep- 
tion of a small admixture of fine sand to secure a smooth finish on 
the face. The method generally employed in monolithic construction 
was adopted — forms of timber were built up and the concrete molded 
in them. Right here is where the trouble occurred. A man experi- 
enced in this method would have realized that the use of wide planks 
in the forms would be objectionable as they would be sure to warp 
when saturated with the moisture of the concrete. This was just 
what occurred. The result is that in many places the concrete walls 
are uneven. This defect might easily have been avoided by the use 
of narrow timbers or "kerfing" in the forms, as would have been 
done by a practical concrete contractor. Despite this the gentleman 
who has superintended the work is entitled to credit for having 
given to property owners a tangible demonstration of the advantages 
of concrete as a building material. It is not everybody who, abso- 
lutely without experience in construction, can put up a building of 



this size that will hold too;ether, and not only hold together, but be 
strong and secure enough to pass an unusually strict and critical 
examination by the official inspectors. 

The cost of this structure is about $35,000. This is virtually what 
the ordinary brick construction with a pressed brick facing would 
have cost. But I do not think it fair to cite this as the average 
result under ordinary conditions. Every beginner is bound to make 
mistakes especially in building operations, and these mistakes are 
always costly. We all learn by experience. I am confident the 
expense of construction would have been considerably less in this 
instance if the work had been done under the supervision of com- 
petent experts. I am also confident that the gentleman himself will 
he able to improve upon the results should he undertake another job 
of this nature, not only in the appearance and nature of the con- 
crete itself, but also in the item of expense. But we should not look 
too strongly upon the matter of initial cost in the erection of our 
buildings, or in any other form of construction where permanency 
is desired. The features of maintenance and durability are of far 
more importance. Wq may be able to erect a certain structure for 
$25,000, while another of exactly the same size but of different 
material will cost $30,000. The former, however, will begin to dis- 
integrate or decay within a comparatively short time and after a 
certain stage will require almost constant expenditure to keep it in 
usable condition, while the latter is unaffected by age or weather, 
and remains as sound and serviceable as when first erected. Which 
is the cheaper in the end? This is the question which property own- 
ers should consider, but I am sorry to say they do not always do it. 

Concrete is the only building material which does not begin to 
disintegrate almost as soon as it is put up. It is the only building 
material which actually improves with age, growing stronger the 
longer it is in use. This is not opinion ; it is cold fact. The asser- 
tion is substantiated by hundreds of tests made by men of unques- 
tioned ability and integrity. Every other material I know of begins 
to show signs of impairment within an alarmingly short time after 
it is exposed to the elements. I make no exceptions. To those who 
may contemplate construction and are interested in the initial cost 
only I will say that wood is undeniably the cheapest, and at the same 
time the most inexcusable and dearest in the end. In a city like 
Chicago, when the fire risk is considered, the use of wood in any 
form of construction is nothing short of a crime. As a general prop- 
osition I think it may be safely estimated that concrete construc- 
tion will cost about the same as the ordinary grade of brick, certainly 
no more, and in some instances a little less. Local surroundings are 
a great factor in building cost. In a country where good lime- 
stone is scarce and clay abundant brick, of course, would be the 
cheapest. This, it should be remembered, refers solely to the initial 
or first cost, which is a very poor basis to figure on. 

Contrary to the almost universal opinion concrete is not a new 
construction material. The ancients utilized it for centuries and 
niany of their works built hundreds, yes, thousands, of years ago, 
still endure. Concrete is new onlv in this country, where until 



recently, we have been indulging in the most extravagant and inex- 
cusable forms of construction. Gradually we are beginning to realize 
our mistakes in this direction. It is now about fifty years, certainly 
not more,sincethe subject was taken up in the United States, but the 
progress has been very slow until now. More has been accomplished 
in the last two or three years than in the preceding forty-five. Archi- 
tects and practical builders are getting into touch with the merits of 
the material, and from now on I look for a very rapid advance in 
its employment. Aside from the question of actual direct economy 
It has the advantage of being fireproof which should commend it to 
all thinking people. This latter feature alone is a matter of serious 
importance in a city like Chicago, where the maintenance of our fire 
department means an expenditure of several millions of dollars 
annually, and is constantly increasing. 



Tensile Strength of Concrete. 



Comparative tests showing the average tensile strength of con- 
crete made with the best of cement and torpedo sand and of the 
same quality of cement and limestone screenings coming from 



crushing machines 



VOLUME OF MATERIALS. 


TENSILE STRENGTH IN POUNDS. 


c 

(U 

6 

U 


C/2 


he 
.S 

"c 

(U 

<u 
a 


Q 


Q 

00 
M 


(A 

c 


en 


I 
I 

I 


3 
3 


3 


300 
300 
410 


400 
450 
580 


500 
65a 
705, 



These averages were taken from the thousands of tests made 
by Robert W. Hunt & Company during the building of the Hib- 
bard, Spencer & Bartlett warehouse and the La Salle street railway 
station, where crushed limestone screenings were used. 

The screenings were taken from the crushers and contained 
chips and bits as large as the largest particles in torpedo sand and 
included the fine dust in the screenings, which showed under the 
microscope to be made up of small pieces each with sharp surfaces 
and more readily bound by the cement. 

The cement and sand averages in tensile strength are generous. 
It is the general rule to find that the screenings and cement produce 
a strength of about 100 pounds more than the cement and sand. 




|t3 



2! 

O 
> 



y. - 






Real Economy in Street Paving. 



No one feature of municipal ini])rovements is of such vital impor- 
tance to all classes of people in Chicag-o as the item of street paving. 
Casually considered it may be thought to affect only the property 
owners who pay the bills. This is a grievous misconception of fact. 
Every person who uses the city highways in any capacity is directly 
interested. It is the natural desire of all that these highways be 
maintained in the best possible condition. Property owners want 
true economy m the form of value received for the large sums of 
money which they pay for street paving purposes, and keenly realize 
the influence which a well-paved highway has upon the prices of 
abutting realty. Every driver of a vehicle, no matter how humble 
its character ; every owner of a team, whether employed in heavy 
drayage or for pleasure purposes, favors conditions which give him 
the easiest and most unobstructed passage. Tenants of business and 
residence structures are keen to the advantages of a substantially 
paved roadway. With this community of interests, it might be sup- 
posed that influence would be exerted by the people of this city to 
secure Avhat is essentially requisite in this line. As a matter of fact, 
however, this is not done. Despite the enormous amounts of money 
expended for street-paving purposes it is undeniable that Chicago, 
with a few notable exceptions, is a poorly paved city. The chief 
trouble appears to be directly traceable to a lack of ordinary common 
sense and business precaution in the selection of materials, and the 
preparation of specifications as to the quantities, manner of laying, 
etc. lliis is strikingly apparent in the down-town section where, 
above all other districts, there is an urgent demand for intelligent 
procedure. Street after street in the business localities is paved at 
great expense without adequate consideration as to the nature of the 
traflic which it must sustain. The result is seen in a short time in 
broken and uneven surfaces which make drayage slow and expensive. 
Property owners wax indignant, and merchants complain of heavy 
financial loss caused by serious interruption of their business. In 
unison they accuse the contractors with doing poor work and in some 
instances with downright dishonesty. This is unfair and unjust. It 
is not the purpose of this article to make any plea or defense for the 
street-paving contractors. They are able to take care of themselves. 
As a rule they will be found to compare very favorably in the integ- 
rity of their business dealings with the people who accuse them. 

As a matter of plain truth the cause of poor street paving may be 
found in the inadequacy of the provisions made for its regulation. 
Owing to the nature of the soil Chicago is a difficult city in which 
to construct solid and durable pavements. This is particularly true 
of the down-town district. In this part of the city there has been 
from time to time considerable filling-in with refuse material. On 
several occasions when excavations have been made for municipal 
works such as sewers or water pipes, the remains of old wooden 
pavements have been found from five to seven feet below the present 
street levels, thus proving that there has been a "fill-in" to this 




< 

< 

< 
/^ 

^ ;^ 

— c 



< Oi 

•J a. 



— 5 



'J 5 



^ fe 
/: 



extent. The natural soil is soft and spongy, and the material used 
in filling is little better. When one stops to consider this, and then 
thinks of the enormous drayage which is daily hauled through our 
down-town streets, many of the loads weighing- from six to seyen 
tons, it would seem that common business sense would secure the 
acme of solid and substantial construction in the payements. But 
this is not done. Ordinary judgment is not exercised either in the 
selection of the surface material, or the laying of the foundation 
which supports it. The one object appears to be to make the paye- 
ments as cheap and flimsy as possible in order to pare down the initial 
cost. The result is painfully apparent. 

It is a well accepted principle of engineering that no structure is 
stronger than at its weakest point. This pertains with full force 
to street payements. No payement is stronger than the foundation 
on which it rests. The street-paying specifications now in effect 
proyide for six inches of crushed stone or crushed-stone concrete as 
a foundation. This amount is woefully insufficient. The quantity 
should be doubled at least if adequate protection is to be secured. 
With from 12 to 18 inches of stone or concrete as a basis the streets 
of Chicago may be put in condition to withstand any pressure which 
may be placed upon them, and to outlast by many years those con- 
structed under the existing regulations. The only objection made to 
this increase in the depth of the foundation is that it would inyolye 
a great additional cost. This is a false argument. Six inches of 
crushed limestone costs 25 cents per square yard. To double the 
quantity would incur an extra expense of 25 cents a square yard. 
For payements which cost from $2.50 to $4.15 per square yard this 
additional outlay would be insignificant as compared with the greater 
durability and permanency thus secured. Measured by the results 
obtained there would be an actual economy of marked importance. 
All surfaces, no matter of what material, would last longer if placed 
upon a solid foundation of this nature and property owners would 
thus be relieyed to great degree from the expense of maintenance. 
Besides this the streets would remain in better condition and business 
would be benefited by the better drayage facilities. No property 
owner with priyate interests at stake would be credited with the pos- 
session of common sense if he were to attempt such false economy as 
now obtains in the paying of our public highways. 

Better judgment should also be exercised in the selection of the 
surface materials. Granite block, yitrified brick, asphalt, macadam 
are all good in their place. Surfaces should be designated with due 
consideration of the nature of the traffic they will haye to bear. At 
present there is no systematic procedure in this respect. La Salle 
street, from the riyer south, for instance, is a striking illustration 
of this utter lack of business method. First we haye seyeral blocks 
of granite surface, then yitrified brick, and then asphalt, all on the 
same street and within a comparatiyely short distance. Each of these 
surfacing materials has its merits but no conditions can be imagined 
by which such a heterogeneous combination can be both seryiceable 
and economical. There is a wide range in the cost of these sur- 
faces. If the cheapest answers the requirements of the traffic on 

93 



that street, then the outlay for the more expensive kind was inex- 
cusable ; on the other hand if the demands of traffic called for the 
more costly variety it was a blunder to use the cheaper grades on 
the same street, and especially in adjoining blocks. 

All streets on which there is an unusually heavy traffic, such as 
those adjacent to railway freight yards, warehouses, manufactories, 
etc., should have a foundation of from 12 to 18 inches of crushed 
stone with a surface of the best granite blocks. Those used for 
mixed business purposes, such for instance as State street, should 
have a crushed-stone concrete base of from 9 to 12 inches with a 
surface of asplialt or brick. In the residence districts the concrete 
base should be 9 inches in dejnh with an as])halt top to lessen the 
noise and facilitate cleaning. There is a considerable part of Chicago 
in which there is a demand for serviceable roads but which is too 




COMCRtTL 



(_.M ii-^ V ^1. 



i\ (iiitlcT witli Aspliiill Pavenu'iit, 









A Macadam Roadway with Ordinary Sandstone Curbint^. 




An AccL'ptablc Plan for Fi^rurint,' the Crown on Roadways, 

sparsely settled t(^ admit of the expense of asphalt or brick highways. 
In these sections limestone macadam will meet the demand admir- 
ably. This is comparatively inexpensive and when constructed with 
a good "crown" (a curve from the center to the curbs that will act 
as a watershed) the roadways are all that could be desired. With 
highways constructed in this manner — witli a strong, substantial 
foundation — we will have much better streets than at present, with a 
lessening in the cost of mamtenance which in itself would be a large 
item of economy. Figures showing the average cost of the various 
kinds of paving per 25 feet of frontage are given in tabular form in 
another article in this book under the heading of "Comparative Cost 
of Street Paving." 

In the making of crushed-stone concrete for street paving, as 
for all other purposes, care must be exercised to obtain a perfect 
mix. Careless workmen can spoil a batch of concrete, or at least 



94 



greatly depreciate its quality, just as easily as the same lack of care 
will spoil or damage other articles. To insure the best results in the 
making of concrete there must be a thorough "mix." Clean stone 
first moistened, must be shoveled and reshoveled through the cement 
until the latter completely covers the surfaces of every particle of 
stone. When this is properly done the adhesion of the mass will be 
perfect, and the concrete will be satisfactory under the severest tests 
that can be applied. Men who understand the process of mixing will 
get better results from i part of cement to 9 of crushed stone and 
screenings than their less careful co-workers will from doubling the 
quantity of cement. In European countries where concrete mixing 
has become almost a fine art, notably in France and Germany, per- 
fect homogeneous masses are made with i part of cement to 15 of 
crushed stone and screenings, and in some instances the proportions 
have reached the high ratio of i to 20. There is no reason why the 
same results, which mean a wonderful lessening in the item of cost, 
may not be had in this country if the same care and diligence is 
exercised in the mixing. 

In considering the subject of street paving serious consideration 




COMBINATION CRUSHED LIMESTONE CURB AND GUTTER AS USED 
IN MILW^AUKEE. 

should be given to the matter of curbs and gutters. The city speci- 
fications provide for the exclusive use of natural sandstone curbs on 
all macadam roadways, and of a combined curb-and-gutter made of 
crushed-granite concrete on asphalt paved streets. This is an 

95 




'A vi 






in O 








injustice to the property owners as it compels them to pay a high 
price for curbs and gutters which are no better in any respect than 
those made of limestone concrete which can be furnished for 30 per 
cent less. There was a time when the use of the sandstone curb 
under some conditions might have been defensible. With the intro- 
duction of the new^ method of placing a bed of concrete under the 
gutter so there is no danger of its being tilted out of plumb by the 
roller forcing the macadam beneath it, this necessity no longer exists. 
The new process is shown in the accompanying illustration furnished 
by City Engineer Poetsch, of Milwaukee, Wis., in which city, after 
a thorough trial of both systems, the combined limestone curb-and- 
gutter had been adopted on account of its pronounced merits and 
economy. So far as the combined curb-and-gutter made of crushed- 
granite concrete is concerned its further exclusive use is indefensible 
if the interests of the people who pay the bills are to be protected. It 
has absolutely no merits which are not possessed by the same article 
made of limestone concrete and has the positive disadvantage of 
being much more expensive. The cost of the former per running 
foot is 65 cents, while the cost of the latter is only 45, a difference 
of 20 cents per foot or $5 per 25-foot lot in favor of the limestone 
product. 



Comparative Cost of Street Paving. 

These figures are taken from actual lettings of work done in the 
city of Chicago. The variation in price is due mainly to local condi- 
tions, such as the accessibility of the job, its size, nature of the street, 
etc. The price asked for a small job is naturally higher in proportion 
than that for a large one. Contractors also take into consideration 
the interruptions they are liable to encounter during the progress of 
a job. For this reason they will ask a higher price for a street on 
which there is a strong probability of delay than on one which will 
admit of the work being rushed. 

Highest Low^est Average 

Material. per sq.yd. per sq. yd. per sq. yd. 

Macadam — all limestone $ -95 $ -85 $ .90 

Macadam — granite top 1.42 i.io 1.26 

Crushed cobblestone — slag base.. 1.33 1.33 1.33 

Macadam — slag base 1.52 1.20 1.36 

Brick — stone base 2.60 2.30 2.40 

Asphalt — stone base 2.95 2.30 2.45 

Granite — stone base 4.13 3.50 3.80 

In striking these averages the usual plan of adding the high and 
low price and dividing by 2 has been discarded as not being fair 
to the various interests concerned. This plan would hold good if 
the jobs on which the extreme high and low prices were obtained 
were equal in number. But this is not the case. The jobs which 
were let for, or close to the low figures, far outnumber those on 
which higher prices were made. Consequently, in arriving at the 

97 



averages the number of jobs let at the various figures has been used 
as a factor in the computation. 

The average width of the paved roadways in Chicago, outside 
of the business district, is 30 feet. This would make 42 square yards 
of paving for every 25 feet of frontage. On this basis the cost per 
25-foot lot of the various kinds of pavements would be as follows : 

Macadam — all limestone $ 37-8o 

Macadam — granite top 52.02 

Crushed cobblestone — slag base 55-8(j 

Macadam — slag base 57-12 

Brick — stone base 100.80 

Asphalt — stone base 102.90 

Granite — stone base .' 1 59.60 

No figures are given for cedar block pavement, it having been 
discarded as impractical in a modern city. Aside from its unsanitary 
features it is the most expensive of all paving material when the 
true tests of durability and expense of maintenance are applied. 

In placing the actual area to be paved at 42 square yards for 
every 25 feet of lot frontage no allowance is made for the street 
intersections, the cost of paving which is assessed pro rata on the 
abutting property. It would be misleading to figure in the cost of 
these intersections as in many instances they have been already 
paved and paid for. Besides this a large number of streets are used 
by the cable and trolley lines which pay for and maintain the paving 
between their tracks, thus reducing the area by that amount. Taking 
the city in its entirety one item will about offset the other, so that 
the only equitable basis for computing the cost is the actual square 
yardage for each 25 feet of frontage. 



Superiority of Limestone Macadam Roadways. 



BY COL. J. HODGKINS. 
(President of Brownell Improvement Co.) 

I am a firm believer in the merits of limestone Macadam road- 
ways in residence districts. Aside from the marked economy in the 
two important items of original cost and expense of maintenance, 
there is a sanitary feature which should commend them to every 
thinking person. Limestone Macadam is absorbent and the objection- 
able odors and other characteristics of animal droppings quickly dis- 
appear. There are great areas in the outlying residence districts 
of Chicago in which the streets are rarely swept or cleaned. People 
who will take the trouble to compare the conditions existing in these 
sections on such streets as are paved with limestone Macadam with 
those on highways of other material will be surprised at the sanitary 
advantages of the former. If cleanliness is conducive of health, and 
I believe this is universally admitted, there can be no question as 
to the advisability of adopting limestone Macadam on all residence 
roadways where the traffic does not demand a highway of different 
nature. 



LcfC. 



Considered solely from the standpoint of economy, which, while 
selfish, is very natural, limestone Macadam has no rival as a paving 
material. There is a large district in Qiicago bounded on the north 
by 63d street, the south by 79th, west by Halsted, and east by 
State, in which the roadways are nearly all of this character. Many 
of them have been in use for fifteen years — some as long as from 
seventeen to nineteen years — with only a slight outlay for repairs, 
these latter consisting solely of resurfacing. When these pavements 
were laid the cost of Macadam was about 75 cents per square foot, 
which meant an outlay of $31.50 for each lot of 25 feet frontage 
on streets of ordinary width. Can this showing be duplicated, either 
in cost or length of service, by any other material? 

It is a matter of pride to me that I was a pioneer in the advocacy 
of limestone screenings as a road-making material in connection 
with the use of crushed stone. As a bond between the foundation 
and surface screenings are unequalled. This is recognized officially 
by the South Park Board and all specifications for boulevards and 
driveways now call for them in place of gravel, which was formerly 
used. The time is coming when they will also be given preference 
for surface purposes. 



Chicago Drainage Trustees Adopt Screenings 

Concrete. 

On the advice of Isham Randolph, chief engineer, limestone 
screenings have been substituted for sand in the making of con- 
crete on Water Power Sections Nos. i, 2 and 3, of the Chicago 
Drainage Canal. As explained in the official correspondence which 
follows, Mr. Randolph made this change for two very good reasons. 
The first is that he has satisfied himself that concrete mixed with 
limestone screenings is greatly superior in strength and durability 
to that made with sand ; the second reason is that there is an actual 
saving of $7,225 on the job of 144,500 cubic yards, or 5 cents a 
yard. The correspondence on this subject is taken from the Official 
Proceedings of the Sanitary District of Chicago, published August 
I, 1904. 

"Gentlemen : For your information, as a matter that should be of 
record, I transmit herewith a copy of an order which I have issued 
to Mr. Joseph Duffy, contractor for Water Power Sections i, 2 and 
3, said order changing the concrete specifications to the extent of 
substituting crushed limestone screenings for sand as an ingredient 
of the concrete. My reason for doing this is based upon demon- 
strations of the superior strength of concrete made with crushed 
limestone screenings, as shown by a series of tests conducted in our 
own cement laboratory, which confirm tests made by others, notably 
by the Engineer of Bridges and Buildings, of the Chicago, Milwau- 
kee & St. Paul Railway, which tests have extended over a period 
of two years. I submit herewith copies of letters received from Mr. 
C. F. Loweth, Engineer of Bridges and Buildings, C, M. & St. P. 

100 



Ry., and from Mr. G. W. Vaughn, Engineer of Joint Track Eleva- 
tion, giving their views upon the subject. It is proper to state that 
the saving to the District growing out of this change is 5 cents 
per yard on 144,500 cubic yards, or $7,225. This saving, however, 
is a very minor consideration when taken in connection with the 
increased strength of the structures as demonstrated by the tests 
in our possession. Respectfuly submitted, 

IsHAM Randolph, Chief Engineer." 

By unanimous consent it was ordered that the communication from 
the Chief Engineer, with the accompanying order to Joseph Duffy, 
and the letters and tabulations of tests made, be printed in the Pro- 
ceedings and placed on file as a part of the permanent records of the 
Board. Following is the order to Joseph Duf¥y, and the letters from 
Mr. Loweth and ^Ir. Vaughn : 

Str — The Sanitary District of Chicago, acting under the provisions 
of Section 64 of your contract with the District, dated October 14, 
1903 (said section relating to "Change in Plan"), hereby notifies you 
that the District desires to change that clause of the specifications 
covering the ingredients to be used in making concrete and to sub- 
stitute crushed limestone screenings for the specified sand. The 
crushed limestone screenings shall be procured from sound and 
clean limestone and no such screenings shall be used unless of a 
fineness which shall pass through a No. 8 sand screen. The pro- 
portions used of screenings to crushed stone and cement shall be 
exactly the same as is called for in the specifications for sand. 
This change shall in no way alter, modify or affect your said con- 
tract of October 14, 1903, save as herein distinctly set forth. Inas- 
much as the substitution herein called for will result in a lessened cost 
to you in the construction of the concrete walls called for by your 
contract, I hereby fix the price to be paid you for the several classes 
of concrete to be built by }ou, in lieu of the prices named in said 
contract, as follows : 

For natural cement concrete faced with Portland cement mortar, 
three dollars and seventy-five cents ($3.75) per cubic yard. 

For natural cement concrete in core wall, three dollars and forty- 
five cents ($3.45) per cubic yard. 

For Portland cement concrete in bridge structures, seven dollars 
and ninety-five cents ($7.95) per cubic yard. 

If you accept this order, please sign the two duplicates hereof 
enclosed herewith. Yours truly, 

IsHAM Randolph, Chief Engineer. 



I hereby accept the foregoing order for the substitution of crushed 
limestone screenings for sand in making concrete and will be gov- 
erned by its terms and conditions. Joseph J. Duffy. 



Chicago, May 4, 1904. 
Mr. I sham Randolph, Chief Eiio-jjicer, Sanitary District, Chicago, 
III.: 
Dear Sir — As per our conversation of a few days ago, I am send- 



101 



iiig- you the original copy of our test report of crushed limestone 
screenings with that of cement. The tests extend over two years. 
They are more clearly shown on the diagram of the second sheet. 

In April of last year a full report of these tests, so far as then 
made, was published, a quite full description being printed by our 
Cement Tester. The report herewith carries this series of tests 
up to two years, and shows in every case but two that the gain 
during the year was at least as good as for neat cement, the two 
exceptions being immaterial. 

I have for a good man\- years been convinced that limestone screen- 
ings and dust was not detrimental to the strength of concrete, and 
had been regulating my practice accordingly. However, it seemed 
desirable to have this belief confirmed by test, and hence this series 
was begun. 

The references Xo. 8 and \o. 4 refer to the numbLM- of the screens 
through which the screenings were passed. 1m ;r comparison, a mor- 
tar made of our standard Hammond sand is sliown. 

^'ours respcctfull)-, 

C. \'. Low i: 111, 
Engitwcr mui Su/^crintciidcui Brid<^cs and Ihiildini:;s, 
Chicago. Milwaukee & S^t. Paul Ry. Co. 



CiiUAc.o. July 2/. 1904. 

Mr. Isliain RatuiolpJi, Chief Jliigi ccr. Sanitary Pisfricl. Security 
Ihiildiug, City : 

1)i:ak Sir — I beg to acknowledge the recei])t of \our favor of the 
22(1 inst., with blueprints showing the result of tests of mortar made 
of cement and limestone screenings. 

Tlie tests we have made using screenings instead of sand show 
results similar to those shown nn the diagram, and J have l^een 
so nuich iiv.pressed with these and other tests which 1 have seen 
that 1 Ikuc used this mixture in i.ur last subway, which has just 
been completed. 

I have been often impn^rtuned during the last three }ears to try 
screenings in place of sand, but persistently declined to do so until 
J had a year's test. I then hecame convinced that it was not only 
safe but that it made a stronger mortar than sand, and as the 
monthly tests showed that the mcrease in the tensile strenoth was 
quite uniform between the 90-day test and that at one year, I became 
convinced and used it at the first opportunity. 

I have no doubt it will be used very extensively in coming years, 
so much so that the ordinary process of crushing stone for ballast 
and concrete will not yield sufficient of the screenings to meet the 
demand. Yours truly, 

G. W. Vaughx, 
Engineer in Charge, Joint Track Elevation, Eighteenth 
Street to Ashlaiid Ai'cnue, A., T. & S. F. R\. Co., 
C, M. & X. Rd. Co., C. & A. Rv. Co. 



\m 



COMPARISON ON BASIS OF PERCENTAGE OF TENSILE STRENGTH. 
SAND TEST TAKEN AS 100 PER CENT. 





UTICA CEMENT— PARTS. 


ATLAS CEMKXT I'ARTS. 


Length of 
Test. 


I Cement, 
3 Sand. 


I Cement. 
3 Crushed 
Limestone. 


I Cement, 
3 Sand. 


I Cement, 
3 Crushed 
Limestone. 


7 days 

i4 days 

28 days 

3 months 


100 per cent. 
100 per cent. 
100 per cent. 
100 per cent. 


150 per cent. 
160 per cent, 
i^i per cent. 
185 per cent. 


100 per cent. 
100 per cent. 
100 per cent 
100 per cent 


183 per cent. 
201 per cent. 
205 per cent. 
200 per cent. 



E. A. MOLLAN. 
Cement Tester, Sanitary District of Chicago. 



Superiority of Concrete IVlade With Screenings. 

In the following table results are given of a series of experi- 
ments conducted by Mr. "Bud" Reilly, laboratory expert for the 
city of Chicago, with the purpose of determining the relative value 
of concrete made with sand and screenings : 









^ 


^ 






^ , , 


^ 


^ 






^ 


^ 


^ <v 


M-l 




U 


(jiii & 


Cen 
ston 
igs 


^ 


-*— ' 


in 


•^ , ^j 


(u .m 


CO 










1^ 


2^U 


^ 5-1 

^ CO 


^ f^ C 


I Par 
3 Lin 
Screei 


At 7 davs ........ 


633 
734 


241 

399 1 


411 


382 

575 


At 28 davs 


At 3 months . 


821 


425 
466 


551 
548 


673 
739 


At 6 months 


859 


At 9 months 


924 


509 


560 


740 


At 12 months 


923 


532 


562 


744 



Mr. Reilly says : ''In all of these tests the limestone screenings 
hive show^n a far superior tenacity and bind than any of the other ma- 
terials, excepting the neat cement. The tests for tensile strength, for 
instance, show what resistance in pull the material will stand. In 
this important respect concrete made with cement, sand and gravel 
has proven unsatisfactory. One block, made with a mixture of 
one part of cement, two of sand, and seven of gravel has almost 
fallen away of itself. It is actually possible to kick this particular 
block into fragments, thus proving that the mixture is wholly inad- 
equate, and that the gravel has a tendency to crumble or disinte- 
grate. On the other hand, concrete made with cement, screenings 
or sand and crushed stone has given entire satisfaction. 

103 



Experiments with Concrete Railway Ties. 

(From the Railway and Enginefring Review, of August 1. 1903.) 

Now that ''aihvay and governmental anthoritics liave become 
thoroughly aroused to the question of a future timber supply, any 
measure undertaken with a view to conserve this supply, increase the 
life of timber that is used for structural purposes, or substitute other 
material, wherever timber is in deniand in large quantities, is neces- 
sarily a subject of a good deal of interest. Particularlv is this state- 
ment applicable to the matter of railway ties. Facts and figures bear- 
ing out the urgency of the situation have been turned over in the 
rninds of railway managements in this country for a number of 
years, with the result that substitutes for timber for ties are now 
l3eing thoroughly studied. 

The man who has labored most persistenly along these lines, so 
far as we are aware, is Mr. C. IJuhrer, roadmaster with the Lake 
Shore & Michigan Southern Ky., at Sandusky, O. Mr. Buhrer's 
experiments with concrete for tic material were begun in June, 1902, 




CONCRKTE RAILWAY rii'.S. 



when a few ties of concrete, reinforced with a piece of old rail 
molded in the top face, with the head downward, were laid in the 
main track of the L. S. & ^I. S. Ry., 2j/4 miles east of Sandusky. 
These wore well, and a year ago ]\Ir. Buhrer laid a rail's length of 
these ties in the main track of the Chicago & North-Western Ry., at 
Allis Station, Milwaukee, Wis. At the Roadmasters' Convention, in 
I\iilwaukee, last September, the attention of the members was called 
to these ties, and many interested parties made a visit to the spot 
to look them over. They stood the winter without deterioration or 
change in any respect, and the C. & N.-W. Ry. officials are much 
pleased with them. The track has remained in good surface and 
alignment, and, according to recent official reports, the ties are ap- 
parently as sound as the day they were laid, and even in better condi- 
tion, for the concrete seems to gain in hardness for many months 
after being laid. 

Encouraged by the promising success of this type of tie, Mr. 
Buhrer decided early this year to conduct experiments on a much 

104 



larger scale, and accordingly arrangnienls were made for trials on 
several other roads. One company which desired particularly to 
make a test of more durable construction than can be afforded by 
wooden ties was the Lakeside & Marblehead R. R. This road meets 
the L. S. & M. S. Ry. at Danbury, O., and runs to Lakeside and 
Marblehead. Near the Junction with the L. S. & M. S. Ry. there is 
a long, sharp curve, the maintenance of which has been quite 
expensive. Over this curve there is a traffic of six passenger trains 
each day, and a very heavy freight tonnage. The wear to the outer 
rail has been excessive, there has been difficulty in maintaining the 
rails in gage, and the services of the section men have been fre- 
quently called upon to adz the ties in order to return the inner rail 
from a canted position. After consultation with Mr. Buhrer and 
inspection of the concrete ties laid the season previously, Mr. C. E. 
Gowen, general manager of the Lakeside & Marblehead road, de- 
cided to lav this curve entirely with concrete ties. The track was 
relaid with new 75-lb. rails to a gage of 4 ft. 8)4 ins., and it is bal- 
lasted with limestone screenings. From all appearances the condi- 
tion of this track is ideal. After being under traffic for some weeks 
the rails have remained in good alignment and the surface seems to 
be as nearly perfect as the art of trackmanship could make it. These 
ties were made at Lakeside, O., by the L. & M. R. R., with ordinary 
labor, under Mr. Buhrer's instructions. 

A stretch of main track on the Pennsylvania lines, near Toledo, 
Ohio, has been laid with reinforced concrete ties of the Buhrer 
pattern, and another lot is being made up for a trial on the Wabash. 
After setting 30 days the concrete of these ties is remarkably strong 
and hard, and wall bear smart blows from a sledg^e hammer without 
fracture. The ties are unloaded by being throw^i from the cars. 
The only precaution taken is not to let one tie fall across another. 
Mr. Buhrer says he has no fear of damage to the ties so long as 
they do not strike anything harder than the ground, and from tests 
of the material made in our presence, it does not appear that they 
are an article requiring- delicate handling. The track laid with 
these ties can be raised and tamped with bars or picks equally as 
feasible as track laid with wooden ties, and a misdirected blow or 
''lick" from a tamping bar does not chip or injure the material. 



Screenings Concrete for Fence Posts and Conduits, 



BY GEORGE GRAHAM. 

For some years past I have been interested in the production of 
telephone and telegraph conduits made of concrete, and after an ex- 
haustive series of tests have settled upon limestone screenings as 
the best possible material to mix with the cement. In this work we 
are now using one part of cement and six of screenings, but I am 
in favor of adding another part of the latter, as I am convinced 
the product will be all the stronger and better. It is only fair to 



explain that, while screenings are unquestionably the best material 
for this purpose, the results attained are largely due to the fact 
that the concrete is tamped inside and out by a pneumatic process 
which insures perfect cohesion, and reduces the product to an in- 
tensely solid mass. I have submitted samples of concrete thus 
made to experts who had difficulty in determining whether it was a 
natural or artificial stone. It cleaves as easilv as natural stone, 
and has a fine, compact grain. The demand is such that we are 
enlarging our plant and will engage in the manufacture of fence 
posts and similar articles in adch'tion to conduits. Concrete fence 
posts are indestructible and can be sold for less than timber posts. 
The average life of the latter is five >'ears, and the marked econ- 
omy of the concrete product ma>' be readil)' seen. 

At St. Joseph, Michigan, I have engaged in the manufacture of 
concrete posts for vineyards, and am now at work on an order for 
500 acres. It is impossible to procure screenings there and I have 
been com])ellc(l to substitute sand, of which there is an abundance in 
that section. These posts are eight feet in length, of which three 
feet is sunk in setting. They arc 4x3 inches at the bottom, and 
4x4 at the to]). Every vineyard man who has investigated the sub- 
ject is readily convinced of lluir suj)eri(irily to timber. 




EFFECTS OF A SLIGHT BLAZE ON -FIRE-PROOF" TILING IN THE 

MASONIC TEMPLE, CHICAGO. 

106 



Crushed Limestone Screenings Test. 



Chicago, Milwaukee & St. Paul Railway Co. 
Office of Engr. and Supt. Bridges and lUiildings, 

Chicago, March 5, 1904. 
:Mr. J. C. Hain. 

Eng'r Masonry Construction C, M. & St. P. Ry., 

No. 192 Fullerton Ave., Chicago. 
Dear Sir: A year ago (March 6th) I sent you one year results 
and comments on a series of Limestone Screening tests. To-day I 
have the pleasure of sending you the two-year results of this very 
interestino- series of tests. 



Pounds Tensile Strength in Curves at A'ariuus Ages. 

bv \Y)lume. 



•Proportions 



Tensile Streng-th^ lbs 



7 Day5<A^ 



3Mo'& 



6Mo'5 



lYea 



2 Years 




Instead of commenting on the remarkable showing for the lime- 
stone screenings as a substitute for sand I have drawn the results 
in pounds of the different mixtures in curves, thinking such will be 



These results of actual strength of the different mixtures is a 
fine view in these curves, and comparing the limestone screening 
results with the sand results is like comparing Portland w'ith nat- 
ural cement. Yours truly, 

G. J. Grisenauer, 

Cement Tester. 



Strength Tests of Limestone Screenings Concrete. 



The tignre; 



given in this table show the results of a number of 
tests made in 1903 by the Pennsylvania Railway with the purpose 
of determinino- the best variety of concrete for use in its track ele- 
vation and similar work in Chicago. The formula of one part of 
cement to three of limestone screenings was decided upon as giving" 
the extreme of strength at the mininuim cost. The tensile strength 
of concrete made by this formula, tlie samples being tested at in- 



tervals 24 hours, 7 d 


a\ s and 2i^ daxs after 


mixing, is shown as 


follows : 






So" 


i" 


i^ 


s f^ 


Zl '~ 




• "— ' -4— < 


■ '- "zr 


. ^ "^ 


^- g t/) 


w F ^^- 


^' r t/: 


^ tU r- 




^ r- 


^ g S - 


1 g| ^ 


5 ^ E 

^ u h -■ 
P ^ "^ >. 


'^ Z: J=: ^ 


^ X -_, ~ 


^ t/: Qj rt 


"t^ *-" ■•7 


r-" u ~ *^ 


-^ u '^ '^ 


aai^T 


l^i ^ 




« roH 


" r^.H 


- roH 


132 


239 


327 


129 


-'4-^ 


342 


T26 


24S 


346 


142 


220 


327 


147 


220 


350 


129 


-'•7 


342 


112 


224 


346 


107 


242 


342 


124 


-M^> 


340 


117 


-'47 


351 


120 


221 


364 


140 


220 


356 


132 


^32 


340 


130 


241 


341 


127 


-'^\^ 


352 


119 


241 


361 


109 


251 


340 


107 


262 


340 


121 


240 


331 


124 


231 


376 



These figures demonstrate a 



ten den c\ 
screenings to gain tensile strength with 
when the stability of construction is taken into consideration 



in the concrete made of 
age, an important factor 



108 



Cost of Sewer Construction in Concrete. 

It is extremely difficult, if not actually impracticable, to arrive at 
any ecjuitable basis of comparison as re^^^ards the relative cost of 
sewer construction in concrete, brick and iron pipe. This is be- 
cause bids are rarely, if ever, invited for the same job in all three 
materials. The engineers first decide which form of construction 
will best serve the purpose and proposals are then asked for on the 
selected variety. Conseciuently there is little or no opportunity for 
competition in price so far as the materials are concerned. Neither 
can any fixed schedule be established as a guide for any one kind 
of construction, even in sewers of the same size. Tn other words, 
it does not follow that because one 5-foot sewer may be built of 
brick at $8.00 per foot that others of exactly the same dimensions 
and material can be constructed at the same price. The size of the 
job, the nature of the soil, the depth of excavation, the accessibilty 
of the work to the base of supplies, are all important factors in de- 
termining the cost. Thus one 5-foot sewer may be built at a profit 
at $7.50 per foot, while on another the contractor will lose money 
at $8.50. As a general proposition it may be set down as a well- 
established fact that concrete sewers are much more durable and 
satisfactory than those constructed of either brick or iron pipe, and 
that there is a marked economy in the first cost, as well as in the ex- 
pense of maintenance, but it would be unfair to attempt to give a 
comparison in any one or two specific instances. 

The city of Chicago is now constructing its first concrete sewer 
of any magnitude on 95th street, from Erie avenue to Cottage Grove 
avenue. The internal diameter of this sewer varies from 4 to 10^ 
feet, with walls ranging from 9 to 10 inches in thickness. A num- 
ber of other concrete sewers of varying proportions are also to be 
constructed in the same neighborhood, notably those on Cottage 
Grove avenue and on 39th street. All of these are part of one gen- 
eral system, and are being built on the advice of Chief Engineer C. 
D. Hill, of the Board of Local Improvements, who has given the 
subject careful consideration. In submitting the proposition in 
his official capacity ]\Ir. Hill said he was convinced that concrete 
would not only give the best satisfaction in this extensive work, 
but that a saving of at least $40,000 will be made in its use. Tak- 
ing a diameter of 5 feet as the basis of computation, ^Ir. Hill fig- 
ures that a fair comparison of cost in this particular instance would 
be as follows : 

Diameter of Sewer. ^^laterial. Cost per Foot. 

Five feet Concrete $ 6.50 

Five feet Brick 8.50 

Five feet Iron pipe i5-00 

But the item of cost in the matter of sewer construction is 
dwarfed by the more important features of durability and satisfac- 
tory service, as is the case in every instance where concrete enters 
into competition with brick and iron pipe on the respective merits 

109 



of the three materials. Concrete sewers are without joints or 
breaks of any kind, being one continuous pipe, smooth on the inside, 
and offering no resistance or impediment to an unobstructed flow 
of sewage. They are not easily affected by uneven pressure or 
strains which throw iron pipe sewers out of phimb at the joints, 
causing bad leaks and necessitating expensive repairs ; or, as in the 
case of brick work, loosening some of the "bats" so they fall out 
of place, endangering the security of the entire structure and fre- 
quently bringing on an entire collapse. 

In figuring on the cost of constructing the various sections of 
the main and branch concrete sewers in the 95th street system Mr. 
Hill accepted tlie following- estimates as being well within the actual 
expense : 

Material. Size of Sewer. Cost per Foot. 

Concrete 3 foot $ 4.00 

Concrete 4 ** 5.50 

Concrete 5 " 6.50 

Concrete () " 7.50 

Concrete 7 " 10.00 

Concrete 8 " i^-SO 

Concrete i) " 14.00 

Concrete 10 " 20.00 

In this job considerable iron pipe will be used at an estimated 

cost of S12.50 per foot for thai of 3-fooi diameter and $15.00 per 

foot for the 5-foot size. 



Voids in Screenings, Sand and Gravel. 

The following table of voids is taken from a blue print furnished 
by the Chicago Telephone Company, and shows the results of a 
series of exhaustive tests made by experts for that company. It 
settles, in an authoritative manner, the superiority of screenings in 
this respect, and explains why the Chicago Telephone Company has 
adopted the latter to the exclusion of sand and gravel in its con- 
crete work : 

Material. Percentage of Voids. 

Limestone Screenings ( Crusher Run) t6 

Gravel 20 

Pit Gravel 21 

F. F. Screenings 22 

Sand 26 

One of the favorite arguments, in fact about the only one 
advanced by those who oppose the use of screenings in our works of 
public improvement, is that because of an excess of voids they require 
a larger proportion of cement than sand, thus making the concrete 
more expensive. The figures here given effectively dispose of this 
assertion, as it is hardly probable that the opponents of screenings 
will care to dispute the findings of the impartial experts of the Chi- 
cago Telephone Company who had in view^ only the best interests of 
that corporation. 

no 



Press of 
The F. T. Peterson Co.. Chicago 



OCT 17 1904 



